Jas the general idea is that the appliance is just that, it runs zimbra and nothing else. You are using the vmware/rpath installation because you want less management overheads. We are meant to keep as much unecessary stuff out of the appliance as possible.
So best install the nameserver somewhere else, maybe on the vmware host? or your gateway?
http://wiki.rpath.com/wiki/Conary
That's the wiki page for the 'conary' software installation in rpath.
good luck
Dallas