As the previous post suggested, use imapsync (or, lmtpinject, if you prefer). You don't want to do a straight copy, since the sql db won't be updated, and the messages won't be indexed for search.
(ii) I currently have a maildir setup using postfix + mysql + courier maildrop/imap/pop. I would like to copy over my user data to start testing out zimbra but I don't see currently how to do this in a simple way.
I guess if someone answered (i), I could easily do transfers over myself. If not, hoping there is some other way to quickly copy things over.