Can I set video output of A6400 to 1280×720p?

[matthias]

Hi everyone!
I am regularly using my Sony Alpha 6400 as a webcam to conduct my online seminars via zoom. It works very well.
Now I need to do it via GoToMeeting for one client.
I connect my camera via the "Elgato Cam Link 4K" adapter to my Windows 10 PC.
In GoToMeeting the video immediately freezes, GoToMeeting is not able to initialize the WebCam.

GoToMeeting says it only supports up to 1280×720 pixels.
My question: Is there any way to reduce the output of the A6400 to this resolution?

As far as I know it is only able to output  1920 x 1080p (HD) or 3840 x 2160p (4K).
Any hints are welcome.
Thanks, Matthias