The short answer
Choose Retell AI if you have engineers and want to own the orchestration layer yourself. Choose Zian AI if you want the whole outbound motion run for you. Retell sells voice-agent building blocks you can sign up for and start using today. Zian sells managed autonomous agents across voice, SMS, email and WhatsApp, and is currently in waitlist beta with no self-serve signup and no published pricing.
Read this with your eyes open: we are not neutral
This post is published by Zian AI. We sell a competing product, so discount it accordingly. The same applies in the other direction. Retell AI publishes its own comparison content, including a competitor overview page headed “See why Retell AI Stands Above its Alternatives”, plus blog comparisons against Vapi, Bland, Synthflow and ElevenLabs. Its Vapi comparison concludes: “While Vapi AI provides a solid developer-first approach, Retell AI is the clear choice for businesses looking for an intuitive, scalable, and feature-rich AI phone agent platform.” Normal thing for a vendor to write. It is also not an independent verdict — and neither is this page. Discount our conclusion exactly the way you discount theirs.
What we can do is be accurate about what Retell publishes, link the exact pages so you can check us, and be honest about where Retell wins and we do not.
What Retell AI actually is
Retell AI is a voice-agent platform for phone calls. Its homepage calls it the “#1 AI Voice Agent Platform for Automating PHONE Calls” and invites you to “Build, deploy, and manage next-generation AI voice agents that sound human, execute tasks, and scale effortlessly.” The verbs matter: build, deploy, manage. You are the one doing them. From its documentation, the shape of the product:
- Agent-building primitives. Either a single or multi-prompt agent, or a Conversation Flow built from conversation, subagent, function, logic-split, call-transfer, press-digit and end nodes, among others. You assemble the behaviour.
- Genuine developer posture. Official Node.js and Python SDKs, a REST API, webhooks, a CLI and an MCP server. The quickstart is headed “Build your first phone agent in 15 minutes”, a fair description of the self-serve experience.
- You can keep your own orchestration. The custom LLM documentation states: “Run your own LLM behind a Retell voice agent. Retell handles telephony, transcription, and turn-taking while your WebSocket server generates each reply.” If your conversation logic already lives in your codebase, that is unusual and valuable.
- Serious telephony. Retell’s custom telephony docs recommend elastic SIP trunking, so you can keep your existing carrier and PBX. Twilio, Telnyx, Vonage, Genesys, Five9, Avaya and Amazon Connect each have a documented deploy page.
- Inbound is a first-class citizen. IVR navigation, AI-to-human transfer, live monitoring, post-call analysis and AI quality assurance are all documented, and the industry pages lean towards receptionist, support and dispatch work.
- Calendar and CRM integrations. Cal.com and Calendly for booking, plus Salesforce, HubSpot, Microsoft Dynamics, GoHighLevel, Zoho and Zendesk, each with its own integration page.
- Broad language coverage. Retell’s supported languages page lists 55 languages, spanning 63 locale variants, across its speech and text-to-speech providers, noting that “Every language your agent uses must be supported by both a voice (text-to-speech) provider and a speech recognition (ASR) provider.” Wider coverage than Zian’s 30+, and we will not pretend otherwise.
Packaging model
We quote no prices, because figures in a competitor’s blog post are usually stale by the time you read them. Per Retell’s own pricing page there are two plans, “Pay as you go” and an “Enterprise Plan”. Voice is billed per minute of conversation, chat per AI message, telephony separately by country and provider, with monthly add-ons for concurrency, knowledge bases and phone numbers. Free starting credits are included, and Enterprise adds volume pricing, SSO and dedicated support.
Compliance posture, and two things to check
Retell’s security and compliance documentation lists HIPAA (noting “A signed BAA is required before transmitting PHI through Retell”), “SOC 2 Type 1 and Type 2”, and GDPR “compliant via AWS infrastructure with a GDPR-compliant Data Processing Addendum”. BAAs, DPAs and EU Standard Contractual Clauses are self-signable at no extra fee, and per-agent retention is configurable “from 1 day up to 2 years for transcripts, recordings, and logs.” The same page points to a Compliance Trust Center for “certificates, reports, and the latest audit status”.
Two details worth raising with Retell directly. The same page states: “However, please note that we do not currently operate services within the European Union.” If EU data residency is a hard requirement, ask. And two of Retell’s own pages do not line up: the homepage says it is “Fully compliant with HIPAA, SOC2 Type II, GDPR and ISO 27001”, while the compliance documentation page lists HIPAA, SOC 2 and GDPR and does not mention ISO 27001. That is a gap between two pages, not evidence either way about the certification itself — the Compliance Trust Center linked above is where a current ISO 27001 report would sit, and we could not render it. If ISO 27001 is a procurement requirement for you, ask Retell for the certificate rather than reading it off a web page.
What Zian AI actually is, including the awkward part
Zian is in waitlist beta. No self-serve signup, no free trial, no published pricing. You cannot build an agent this afternoon. If you need something running this week, Retell can do that and we cannot, and no amount of positioning changes it.
Zian is the opposite shape of product. Not primitives you assemble, but managed autonomous agents that run an outbound motion end to end: the call, the follow-up, the reschedule, the show-up chase. Two named systems do work a build-your-own team would otherwise write and maintain. SmartReach AI orchestrates which message goes out, on which channel and at which time, adapted by country, industry and prospect profile, with follow-up pacing built in. PrecisionPitch AI split-tests scripts and approaches continuously against real outcomes rather than surface metrics.
Zian runs across voice, SMS, email and WhatsApp rather than voice alone, supports 30+ languages with voice cloning, integrates with HubSpot, Salesforce, HighLevel and Zapier, and can be deployed as a private model on the customer’s own infrastructure. That last point is the sharpest structural difference: a different deployment topology, not a different feature.
The operating history behind it: Zian has been running outbound acquisition since 2017, at one point operating campaigns for roughly a hundred businesses in the same vertical simultaneously. The learning engine tracks around 420,000 data points across more than 10,000 leads a day. It has taken accounts from roughly 2% conversion to around 8%, and in some cases beaten a client’s existing system by five times. First-party figures, no external auditor attached. Weigh them as such.
The decision table
| Your situation | Better fit | Why |
|---|---|---|
| You have engineers and want to own the conversation logic | Retell AI | Custom LLM over WebSocket lets your orchestration drive replies while Retell handles telephony and turn-taking |
| You are embedding voice inside your own product | Retell AI | SDKs, REST API, webhooks, MCP server and web-call widget are built for this |
| You need something live this week, on a card | Retell AI | Self-serve signup, documented 15-minute quickstart; Zian is waitlist-only |
| You want an outbound result, not a platform to run | Zian AI | Managed agents run the sequence; no orchestration layer to build or maintain |
| Follow-up must continue on SMS, email and WhatsApp, not just voice | Zian AI | Multi-channel by design; Retell’s SMS is documented as limited to US numbers |
| The model must run on infrastructure you control | Zian AI | Private model deployment on customer infrastructure; Retell’s docs describe a hosted service |
If your answer is several rows on both sides, that usually means you are really deciding whether to build or buy your AI agent stack, not which vendor to sign.
Where we would genuinely send you to Retell
You have engineering capacity and want control. If your team can own prompts, flows, function calls and failure modes, a platform that exposes primitives beats a managed service. Your marginal cost of building is low, and your appetite for someone else’s opinions is lower.
Voice is a feature of your product, not a channel for your sales team. If you are shipping voice inside software your customers use, you need an API and SDKs, not an agency-shaped service.
Your problem is mostly inbound. Reception, support triage, order status, dispatch. Zian has receptionist-style agents, but Retell’s documented depth on inbound handling and IVR navigation is aimed straight at that job. We covered receptionist versus autonomous sales agent separately.
You want to evaluate today. Waitlists are a real cost. If your evaluation window is two weeks, pick a vendor you can test in two weeks.
On the latency numbers you have seen
Retell’s homepage states that “The platform features a ~600ms latency (industry-leading responsiveness)”. That is Retell’s figure for its own platform. We publish no competing number and no head-to-head. We have not run a controlled test against Retell, so any figure we produced would be marketing dressed as measurement. Treat the latency and accuracy tables in affiliate roundups the same way: almost none publish a methodology, a call sample size, a network baseline or a date, and without those a millisecond figure is a claim, not a measurement. If latency is decisive, run your own calls on your own numbers, from the countries and at the hours you actually dial. Retell documents how to check actual latency in its dashboard, which beats anyone’s blog table.
How we sourced this
Everything above about Retell AI comes from Retell’s own website and documentation, read on 28 August 2026: the homepage, the pricing page, the competitor comparison pages, and the docs at docs.retellai.com covering compliance, SDKs, custom LLM integration, telephony, language support, SMS and the quickstart. We used no affiliate roundups or listicles, which are largely SEO inventory and frequently misstate both pricing and capability.
What we could not verify: any independent, methodologised benchmark of latency, accuracy or booking rate for either platform. None exists that we could open. Nor Retell’s current ISO 27001 status: it appears on the homepage but not on the compliance documentation page, and Retell’s Compliance Trust Center, where certificates and audit status are published, did not render for us. Ask Retell directly. Zian figures here are first-party operating history, not externally audited. Retell figures are Retell’s, attributed and linked.
FAQ
Is Retell AI a direct competitor to Zian AI?
Partly. Both put AI agents on live phone calls. But Retell is a developer platform you build on, billed per minute of usage, and Zian is a managed multi-channel service that runs an outbound motion for you. Teams shortlist them together, then find they are choosing between two purchase types, not two versions of the same one.
Can I sign up for Zian AI today?
No. Zian is in waitlist beta: no self-serve signup, no free trial, no published pricing page. You apply, and access is granted in cohorts. If you need to be live immediately, Retell offers self-serve signup with free starting credits.
Does Retell AI publish its pricing?
Yes. Retell’s pricing page shows a “Pay as you go” plan and an “Enterprise Plan”. Voice is billed per minute, chat per AI message, and telephony separately by country and provider, with monthly add-ons for concurrency, knowledge bases and phone numbers. We do not reproduce the figures because they change; read the source.
Can I bring my own LLM and orchestration to Retell?
Yes, and it is one of the strongest reasons to pick it. Retell’s custom LLM documentation states: “Run your own LLM behind a Retell voice agent. Retell handles telephony, transcription, and turn-taking while your WebSocket server generates each reply.” If your retrieval pipeline or agent loop already lives in your code, that is a clean split of responsibilities.
Which platform handles SMS follow-up outside the United States?
Retell’s SMS documentation states that “SMS (A2P 10DLC) is limited to US phone numbers, excluding toll-free numbers”. If your follow-up needs SMS in Australia, the UK or elsewhere, check that against your plan before committing. Zian’s agents work across voice, SMS, email and WhatsApp as one sequence rather than separate products.
What rules apply to AI outbound calls in Australia?
The same rules as any other telemarketing call. The Telecommunications (Telemarketing and Research Calls) Industry Standard 2017 applies to anyone making telemarketing calls to Australian numbers, whether or not the number is on the register. Per the Do Not Call Register industry standards page, telemarketing calls are permitted 9:00am to 8:00pm on weekdays and 9:00am to 5:00pm on Saturdays, with no calls allowed on Sundays or national public holidays, unless the consumer has consented to being called at that time. Callers must keep calling line identification enabled and terminate a call immediately when asked. Neither vendor enforces this for you by default, so whoever you pick, configure it. More in our guide to compliance for AI outreach.
Should I trust a comparison written by one of the vendors?
Not on its verdict. Trust it on its citations. Retell writes comparisons concluding Retell wins; we have written one concluding Zian wins for a specific buyer shape. What is checkable either way is whether each claim links to the other vendor’s own documentation, and whether that page says what the post claims. Every external claim here links to a primary source. Open them. For the wider field, see our roundup of AI voice agents for outbound calls.
Where to go next
If you have engineers, want to own the orchestration layer, are solving an inbound problem, or need to be testing by Friday, go to Retell. That is a real recommendation, not a courtesy.
If you want the outbound motion itself run for you across voice, SMS, email and WhatsApp, with script and timing optimisation running continuously and the option of the model sitting on your own infrastructure, that is what Zian is built for. We are in waitlist beta, so the honest offer is a conversation and a place in the queue rather than a login. Apply For Partnership and tell us what you are trying to book.