My brief searching on the Zimbra forums suggested that the whole Zimbra service can be stopped relatively easily (a single command) although I don't recall what it was OTTOMH. From what I gathered, and assuming that the TKL appliance is set up similar to a default Zimbra install, a complete backup is as simple as stopping the Zimbra service, backing up the complete contents of /opt/zimbra and restarting the Zimbra service.
If I were you I'd set up another Zimbra instance and do some testing. You could even try rsyncing the /opt/zimbra directory across to another instance so that you have a somewhat 'real world' test environment. Once you have it all working as you'd like, then you can do your real server.
You should be able to stop Zimbra without stopping the machine
My brief searching on the Zimbra forums suggested that the whole Zimbra service can be stopped relatively easily (a single command) although I don't recall what it was OTTOMH. From what I gathered, and assuming that the TKL appliance is set up similar to a default Zimbra install, a complete backup is as simple as stopping the Zimbra service, backing up the complete contents of /opt/zimbra and restarting the Zimbra service.
If I were you I'd set up another Zimbra instance and do some testing. You could even try rsyncing the /opt/zimbra directory across to another instance so that you have a somewhat 'real world' test environment. Once you have it all working as you'd like, then you can do your real server.