I can now happily report that it works. It ain't perfect yet, a reoccurring event is not synced. But it's just disabled in the 0.97 version of the connector.

So now you can sync your mails, contacts and calendar items without any problem. Zimbra OS is now a full alternative for some expensive piece of crappy software sold by some redmond company.

wolfroma released a funambol connector for Zimbra (link). It's reported to work with Funambol 6.5, Zimbra 5 and a Nokia E61.

I installed it already, but for me it didn't work just out of the box. If I find time, I'll get to the debugging part and give an update here