For some reason, I can't figure it out.
I'm running it on Ubuntu 6.06LTS, but for some reason dpkg -l|grep zimbra
or grep for zcs doesn't show anything.

I've tried to look through some of the files under /opt/zimbra and now luck.
I did have the packages listed at one time, but during a rebuild of the machine I think I just copied the /opt/zimbra dir back with out going to the trouble of a base setup first, so no packages listed in dpkg.