How to _actually_ close the app

This program violates standard windows UI protocols:  it refuses to close when the "X" in the upper right is clicked.
This is the same scammy behavior we have seen from malware,  viruses and other apps that try to take control of the system, disregarding the user's desires.  There is another thread on this topic, but it was closed with the resolution "by design", which is a terrible answer and shows this company does not care two wits about it's users.

Until such time as this company decides to follow standard UI protocols, we must take matters into our own hands...

Create a batch file on the windows desktop that contains this line:
taskkill /F /IM zoom.exe /T

Execute this bat file when you are done with your session and it will force Zoom and all child processes to close immediately.
It is quick and it works well.