I have been having issues using my webcam on Zoom. It works at first for 30 to 60 seconds then it starts flickering as shown in the picture. I tried buying an external webcam but it still has same issue.
Have you tested a different application like the built-in camera app? Did you validate that Zoom was using the new camera in your tests? If the issue is solely with Zoom then remove and re-install would be advised.