I took a quick look at the website, but couldn't answer my question quickly. Is Zulip suitable for integrating into an existing application where everything happens within the app?

I am working on an application that needs chat and user-to-user messaging and it needs to happen in the app. Options like Slack, Discord, Mattermost aren't suitable.

This really isn't something I want to write from scratch. .NET Core based App FWIW.