Using a mic plugged into the mac works fine and identified in both mac sound settings and in Zoom audio dropdown. It works for about 1 second, then switches to the built in mac microphone, but no change shown Zoom's drop down.
Latest Mac update might have trigger this problem.
Bottom line, can't use any external mic source at all anymore.
I have a client who is having a similar experience. The have an M1 Mac mini running Monterey, a Logitech webcam with microphone and external speakers attached to the 3.5mm jack. The Zoom call works for a variable amount of time (maybe 20 mins) and then the microphone cuts out.