Does anyone know the syntax for getting an authenticated https Zimbra calendar into Google Calendar? I've tried half a dozen different variations and nothing seems to work for me.

Code:
https://user:pass@zimbra.server.name/home/username/Calendar
Code:
https://user:pass@zimbra.server.name/dav/username/Calendar
Code:
https://user:pass@zimbra.server.name/home/username/Calendar/?fmt=ics
...etc....nothing works. I'm thinking maybe Google won't handle an https calendar URL?