I've got a centos 4.4 box with zimbra - 4.5.2_GA_699.RHEL4 (Open Source)

I want to migrate this to another piece of hardware with centos 5.0 and Zimbra zcs-4.5.7_GA_1319.RHEL5 (Open Source)

I'd like to do the transfer between hardware with rsync, what would the best way to go be to move all my configuration and mail stores between both versions and OS's?

Upgrade the Centos4 version to the latest, then transfer? The open source backup/restore settings indicate how to recover on the same server. Hints? Tips?

Thanks for your time.