I ran into the problem about not being able to run Outlook Rules automatically when using the ZCO. It wouldn't have been much of an issue, but we have one user who insists upon keeping all his mail in a local folder store, rather than on the server. Since Zimbra rules will not move mail to local folders (they should, and I've voted for Bug #29901), this user still needs to use Outlook Rules. I found the following page that describes how to schedule a VBS to run the rules:

How to schedule outlook 2007 rules to run at specific time | Windows Reference

I've got this to work on Win XP and Win 7. Have not verified on Win Vista yet. Hope this helps!