I have not been able to get my calendar to sync with CalDAV either on iCal on the Mac or Thunderbird-Lightning on Linux. On the Mac, iCal says that it can find the server but the username/password is not accepted. I am, of course, using the same username and password as here on the Zoho site. Lightning says that the calendar is temporarily unavailable.
In continuation with our previous post on all the exciting updates and improvements that have shaped Zoho Calendar over the past 12 months, Lets delve into more: Bring your calendars together- Introducing Zoho Calendar and Outlook calendar synchronisation