There are some known bugs with contact synch - here is one that's in bugzilla and is supposed to be fixed for zd 2.0.
Bug 38817 – Google contact sync failure if no contacts exist
I was not able to determine if another possibly related bug re contact sync is already known.
That is that any contacts I enter into zd never make it up to gmail. The other direction is fine; a contact entered into gmail is copied to zd quickly.
The bug applies to both plain gmail and google apps accounts. For all of these accounts, "Synchronize all contacts and groups" is turned on.
Is this a known bug? I'd imagine many have run into it.