Suddenly too tiny a font on screen - Help!

In trying to copy/paste, I suddenly took the screen down to so tiny a font that I cannot see how to undo it - and every known key stroke is not working.  Even closing and reopening does not help. (So, control/z is no longer an option.) Only QB is affected - and only on my computer - not a colleague's.  So - Help me, Obi Wan Kenobi - you're my only hope!  (Thank you in advance.)