I have 2 separate Zoho one licenses for my 2 businesses.
Also, from time to time I'm connecting to a client's User for a period of time when developing.
Sometimes I need to log into a client's Account for a short period of time for support.
The way it looks now, all of these all of Zoho Mobile apps are bound to use only one user at a time.
Please consider Enabling using each app with a few users and to be able to switch between them just like Gmail or whatever.