Hi there. I was one of the unlucky ones who simply exported the local folders on ZD1, uninstall it, installed ZD2 only to find that I couldn't import the original backup.
After some tests I thought that maybe the .META files included in my backup were the reason of my problem, since there's an advanced option to specifically avoid copying them. So I
- uncompressed the backup
- removed all the .META files (one for each message)
- used 7zip freeware to compress a .TAR file
- once again used 7Zip over the previous file to get a GZip file
- renamed the file's extension to .tgz
- imported the backup
UPDATE: this "workarround" still has two problems:
1. (Very important) you no longer have the original mail received date
2. If you back up a folder with many messages, it is divided in many folders with 500 messages each.
Hope someone ellaborated a better way to solve this...