If you are planning on sending a zoom meeting through your switcher and then on to either records/projector or rtmp stream, this is how we do it:

1.Open zoom in on a second computer and check the "two monitor" option which you will find in the zoom video settings. Also make sure your Zoom control bar hides when you go full screen (another setting in Zoom)

2. Your computer should recognize your switcher as a monitor. Just then go full screen with the zoom window you prefer to send to the switcher.

3. If you are planning a two way zoom session you will need to be sure the audio is set up correctly. You don't want your zoom people hearing themselves back or it will create an echo. For large shows we use an audio mixer and send the 2nd laptop audio to that then return the feed back to the laptop but we send an aux back that does not have that laptops' audio ( this method is called Mix Minus ). Alternately, you could just use headset microphones on both ends.
4. From here send the output of the switcher to an encoder/capture device HDMI or SDI to USB so you can bring it into your 1st computer.

5. In your streaming software (Vmix, OBS, Wirecast, etc...) you can add your capture device as a source and you are good to go!