by Ken Task.
Yeah, renaming .zip to .mbz won't work ... mbz no longer means 'moodle backup zip' but it is gzipped (a linux compression). Plus the unzipped must have what moodle expects ... a moodle_backup.xml file as well as a questions.xml file - those are roadmaps to restoring - and I doubt Blackboard would be so kind.
Have no first hand experience with what you are requesting .... maybe others could be specific.
However, having said that, maybe this Youtube video will help
www. youtube. com/ watch?v= uo- aslSWvOQ
'SoS', Ken