FWIW,
I've been using TB for over six months now and I haven't been to happy with it because of some of the same problems described here. To make the story short, when you accept a calendar invite it does not get added to Lightning and it is because of a conflict/bug with one of the add-on I'm using : "Provider for Google Calendar" or "gContact Sync". There is a bug filed somewhere in the TB forums. It does gets added to the Google calendar and then to my iPhone though.
Anyways I wanted to give ZD a shot and I installed it today. I followed some of the suggestions for adding a calendar and having it to sync with Google calendar but I think I made a mistake when I copied the URL but it is working anyways. Maybe the "accidental" mistake is a workaround that solves the issue with calendar syncing; maybe I'm wrong. This is what I did:
Disclaimer: This is working for me but it does not mean it will work for you. If it doesn't please don't come back saying nasty things about me being "whatever", OK?
- After I set up the IMAP account with ZD I went in to the calendar tab and clicked on the drop down arrow for "New" and from the list selected "Calendar"
- I gave this calendar a name, selected a color and check the box "Synchronize appointments from remote calendar". This opens a box for a URL
- Now, this is important. I've read that here you must paste the URL for you iCAL calendar from Google once you get it from the settings. What I accidentally did was to copy paste the HTML URL instead of the iCAL. I realized the error later but decided to try it anyways.
I tested the following with complete success:
- Creted a calendar item in ZD and it appeared in Google calendar
- Created a calendar item in Google and it shows up in ZD
- Deleted from either side and gets deleted in the other end
- Send an invite from inside TB and Outlook and accepted it in ZD which adds it to the Zimbra (local copy of Google) calendar as well as to the Google's one
- Sent and invite from inside ZD to an Outlook 2010 recipient and it adds the invite to Zimbra (local copy of Google) and waits for the accept to add it to Google calendar. About this last action I'm not sure since I don't know if I waited long enough for the item to be added to Google. After taking longer than previous tests I decided to go to the Outlook recipient and accept the meeting. When I came back to Google calendar (in Gmail) it was added.
Maybe I need to do more tests but I'm definitively moving from TB to ZD since it looks like it works for me.
Next is the contacts. On the contacts side I tested the following:
- Added a contact in ZD with two phone numbers, email, address and company details. Everything gets added in Google contacts except address (I didn't expect to do so; I've read a lot of programs having issues with the way address fields are handled in Google. TB has the same issues)
- Added a contact in Google with same fields and it gets added to ZD except for the address.
- Deleted on both sides and it gets deleted in the other end.
- Finally I opened an existing contact, added a phone number and it gets updated in Google. Didn't do the opposite but I will test it as well.
So there you have it. ZD is syncing both calendar and contacts (albeit not completely) with my Google account. I will also test how Zimbra deals with more than one IMAP and POP3 accounts, since I'm currently managing three IMAP and two POP3 in TB.

