Seems like a common issue.

Users in a thread on Microsoft forum say making changes using Skype's settings solve the problem when using Zoom etc. See if anything there helps you...

Thanks Ron.  Using Skype is a good work-around.  With Zoom opened, it is possible to open Skype and go to Settings (via three dots).  Choose "Audio & Video".   The box showing the output of the camera will/may be black because only one app can use the camera.  Click on "Webcam settings".  A nice Properties box pops up, and you can change the settings and see the impact on Zoom simultaneously.  You can leave the Properties box up in case further changes are needed. (In this case, you might set your Skype activity level to "Do not Disturb".)  Or, you can close down Skype -- but do not sign out or quit. Naturally, you might wonder why Microsoft does not make it easier.