I can think of two options:
- Set a simple password on the Quiz and give this password at the start of your Zoom call. How to docs.
- Slightly more complicated: use a combo of access restrictions and activity completion:
- Set up a Page with instructions (or something else useful). Under "Restrict access" add a "Date" restriction for the page to only be available until 5 minutes after the quiz has started. Under "Activity completion" set "Student must view this activity to complete it".
- In the quiz, under "Restrict access" add a "Activity completion" restriction where the page must be marked complete.
- Instruct the students in the Zoom call to click on this page to access the Quiz. It might help to add a link to the quiz in the page as well (purely for user experience).
This should ensure student who turn up late can't access the quiz, but doesn't penalise those who have to come out of the quiz and back in if they have network issues.