Friends, I was able to stop the “green screen” problem described in this thread by turning off (un-checking) all of the hardware acceleration options in the video settings of Zoom.
They can be accessed through the video settings of an active Zoom meeting. Click on the “Advanced” button after opening video settings, then un-check all three hardware acceleration options.
I am suspicious that this has recently become a problem with Zoom for reasons unrelated to ManyCam. I have read that Zoom has made some compromises on its ability to handled HD content, in order to keep up with the growing demand for basic videoconferencing services. The use of hardware acceleration might be pushing a stream into Zoom that it cannot handle. Just a speculation.