Sync shared calendars with CalDav?

Sync shared calendars with CalDav?

Problem:

User A shared his calendar (edit priviledge) with User B.
User B has to be able to edit the shared calendar entries on his Android phone.

The sync with CalDav or DroidDav only shows his main calendar. The shared calendar neither appears in calendar.zoho.com under settings/sync.

We need a way for multiple users to be able to work (create/edit/delete) on the same calendar from their mobile phones. How do we solve that?

Thanks!
Roman