Did you check your manual on P34, P292 and P926?
Yes. The hint is that you use an HDMI micro to full size cable to connect to a screen or other input device - I prefer a screen and have used it also with a data-show. If I am using a computer connected to either device, I just switch HDMI inputs of the screen/datashow between the computer and the camera as required. I have not got such a cable specifically for the R5 myself, but it has worked with every other Canon model I have used. I teach photography and it's a great tool for showing menus and the impacts of changing aperture, ss and ISO.
If you the HDMI port of your computer is an OUTPUT device you MUST connect direct to the display device, as per the comments on P 495
Unfortunately, connecting the camera to a monitor or projector will not work in my situation. I need to show the camera's display in a window on my PC screen so I can show it to others in a Zoom meeting. I suspect that what I need is a device that will convert the HDMI output from the camera to USB that I can connect to the PC. I would then need software that would display the video coming in on the USB port. Specifically what the hardware and software would be I do not know. Thanks for your help.
OK. If this is a one-off - connect your R5 to a TV or computer monitor via HDMI. When you want to display the demonstration involving the camera, have a means to be able to point the webcam you are using at the screen, and that should get you around the issue.
I just modelled this myself with another camera to confirm it works and it does. The image below was taken with my webcam of the TV, into which a 5DMkIII was attached. You can see the screen displays all the details - it was hand-held, so bit wonky, but if you have something to attach the webcam to or can place the screen (it could be your own separate monitor for that matter, if it has an HMDI input) in a position to keep the webcam steady then you're in business.
That depends on whether the computer can accommodate one. For a one-off that's not necessary. The system I oulined above works - I just tried it.
Only cost is $20 HDMI USB capture card that does give the "cleanest" video with smallest footprint. Getting a TV near the computer or 2nd monitor with HDMI input and positioning a webcam within reach may be more work to setup than a simple capture device and free software. This also gives the OP the flexibility to connect a mic and pre-record the HDMI capture via OBS (save stream to disk). My solution meets the OPs desired setup.
I don't disagree. 🙂 The question is whether this is a one-off or not. I would not bother for a one-off, but certainly your solution is effective if this is going to be repeated.