Hey Zen,

We actually have a use case where we do this. One of support teams has a home grown, "light" website, that connects to many systems via API and pulls in information. So they don't have to log in to many places.

It can 100% be done via API to connect to Zendesk.

We first focused on ticket creation from our website to Zendesk Support.

We made sure all the fields and forms were created first.
We kept the fields all as text only.
The field conditions and field restrictions (like length, numbers only, etc) we built into the website and not Zendesk. Allowing for this to be easier to change in the future.
On submitting from the website the ticket is created and we still route to a GROUP.
All the Agents still need to have access to Zendesk and be part of the right GROUPs, as this drives proper access controls (they dont actually log in to Zendesk Support, but we keep that logic in Zendesk side and pulled via the API by the website).

Then the next step for us was how to view tickets and manage them.

This is where we could build it anyway we wanted look and feel, but we made sure Zendesk Support was the source of truth for access controls. If Agent A is part of GROUP X, then they can see these tickets.
Also to protect your API, we introduce manual refresh and a 15 minute auto-refresh. So the agent can choose to trigger the refresh of tickets.

Hope this helps