Can you enlarge a past recording?

 We just did a Zoom meeting and recorded it.  This is the first time that we have a small visual within a large black frame.  I did not intentionally (and I don't believe accidentally) changed the settings.  Perhaps Zoom in an upgrade made an adjustment.  In any event, would you know if it is possible to enlarge a past recording?  And, how do we avoid this in future?  Thank you.