Interesting part about Zulip is it is really amazing for less frequent users. I usually come back to 3000+ unread messages and catch up on all conversations that I find relevant (thanks to stream>topic hierarchy and Recent Topics view).
Also, its trivial to have multiple teams on the same Zulip org, people are just subscribed to different sets of streams. So, say you have two teams: mobile and desktop, for example. You can have streams prefixed with that name:
#mobile-hangout
#mobile-issues
#mobile-support
OR
#m-hangout
#m-issues
#m-support
Good conventions for stream naming makes it really natural for multiple mostly isolated teams to exist on the same Zulip org, and share some streams like #announce, #general, etc that everyone is subscribed to.