ZCS is the server. I'm asking you the version of the Zimbra server that you're connecting to.
You may be getting ZCS mixed up with the Zimbra iSync connector. However, if you are using Leopard (MacOS 10.5) then it doesn't really matter to iCal if you install the iSync connector or not. All it does is configure your CalDAV setup for you.
I dug up a list of files/directories which I've deleted in the past to clear up issues; this
might help:
http://www.zimbra.com/forums/isync-c...rors-ical.html