i got sitecopy to work synchronizing zimbra's calend and contacts.
the output is a large number of ics files (one for every event) and a large number of vcf files (one for every contact). it doesn't seem to be synchronizing as it downloads everything everytime i run it, but i feel like maybe with the right flags, i can get it to actually synchronize.
the vcf files seem portable as there might be a way to merge them all into one file and import them back into zimbra or some other address book that supports them.
their is definitely an ics merge tool out there as well that will merge all the ics files into one, so there seems like a clear path to importing those as well.
overall, i think sitecopy comes pretty close to what i need. i am not ready to run it nightly just yet, but i think to make snapshots every know and then of my data, it comes pretty close.
in case anyone wants to know, here is the config file you need to set up for your zimbra server if you want to use sitecopy
'name-of-share' is the name of your address book or the name of your calendars. if you use the default zimbra ones, they are just 'Calendar' and 'Contacts'
#password or sitecopy can prompt you
you can include multiple blocks of the above config so you can sync multiple calendars/addressbooks in one go.