Zimbra & OD

Hello all, I was wondering if someone on the forums had any prior experience with integrating Zimbra (Running on CentOS) with Open Directory. We'd like the OS X Server to get it's directory information from our Zimbra server. I assume we'd be using the "Connected to Directory System" in the Open Directory preferences. Is this possible? Then, we would use the Mac OS X Server as a VPN gateway. Any help would be greatly appreciated. Thanks again.