Hi,
me an some work colleague have the same problem.

Wie Sync the calendar with iCal using CalDev. So the sync starts and I get every person who has a calendar in an arbitrary order (in Zimbra it is at least sorted by alphabet).

Well if you sort them in iCal, when it syncs again, the sorting is gone, thanks!

Then we keep receiving every alarm every person sets in zimbra, with 50+ people using it, very annoying. Well then I found out, you can disable it for every person (question: why is this not disabled as default?). So I did it 50 times, only to find out, that after a short while, everything was forgotten again... so basically there is no proper way to use the iCal integration right now.
I dont know if it is a iCal problem or Zimbra or both, but is there a workaround? at least for not getting every alarm people set in Zimbra.