Configuration History:
Started with Split Domain, this is a fair amount of work.
Migrated everyone over to Zimbra.
GAL was pulled from both Active Directory and Zimbra.

I think this will be fixed it Version 4.5, but as of 4.0.5...
Outlook Connector and Shared Calendars...
When adding a calendar to Outlook the GAL has their email address not their Logon account.

List has shows up in the list but their real logon account is.

In the admin screen of zimbra switch to Zimbra GAL only (note: we are not in the Authentication screen)
Then add the shared Calendars, it will work.

I have not tested what happens when I switch back to Both. I'm keeping it on Zimbra.