Follow up ...
If you have other content in that backup that you'd like to restore, you could try this ...
A backup without any quiz/question bank still has a questions.xml file.
Looks like:
<?xml version="1.0" encoding="UTF-8"?>
<question_categories>
</question_categories>
You could delete the questions.xml file then create a new questions.xml file which consist of nothing but above.
Then recreate the .mbz ... inside the directory or folder with the uncompressed backup, which looks like:
activities
badges.xml
completion.xml
course
files
files.xml
grade_history.xml
gradebook.xml
groups.xml
moodle_backup.log
moodle_backup.xml
outcomes.xml
questions.xml
roles.xml
scales.xml
sections
users.xm
Issue:
tar -czvf backup.mbz ./*
On a mac or Linux. Dunno if possible on Windows.
The resulting backup.mbz file can be restored ... minus the quizbank/questions.
'SoS', Ken