by Ken Task.
We seem to be providing a little more info not disclosed before. Makes for a lot of back and forth .... new: "Alberta Moodle Hub" and built on 2.8. So they should be restorable to any version Moodle @ 2.8.builddate or higher.
When you unzip via 7zip ... does that automatically recognize (correctly) a gzipped archive? Makes no diff about the extension .mbz. Don't know one can rezip a broken .mbz (the error 'unexpected end of data' means the HUB courses for download are broken to begin with ... duh! Obviously.
Since the source is a HUB, is the Alberta HUB public? Can I acquire a backup from that HUB?
If so, please send URL to HUB and the specific course you were attempting to download and restore.
'spirit of sharing', Ken