Have you tried using the Pick All Instances? Then add Is Overlap below it.
Pick All Instance Monster
Is Monster Overlapping Square = > Zoom in
Alternately, you can do something like a counter with a variable "MonsterOnSquare=0", then have it +1 each time a Monster overlaps or collides with square. So if there's 6 monsters, you can do a command that checks:
MonsterOnSquare = 6 (or greater) & Player is Overlap Square => Zoom in.
You'll need a -1 to that variable everytime a monster is off the square or dies. etc.
It's a little outside the box thinking. Hope it helps.