my laptop overheats and shuts down whenever I use Zoom. It never overheats at any other time.

Video a "compute-intensive", and Zoom is mostly video.  You might try ways to reducing video:

You can "Stop incoming video" from the upper right corner View button.

It might be enough to just use "Speaker View" and not "Gallery View".  Also, if using Gallery View, be sure you have 25, not 49 selected (your computer probably won't let you do 49).

And don't use a virtual background... that also adds to video processing and "heat generation".

Good luck!