Change webcam image from landscape to portrait?

I'm using a generic usb webcam with my windows 10 desktop for video 
conferencing using zoom.  I know I can rotate the image, or change to a 
mirror image, but I've found no setting in Windows, my Nvidia video 
card's "control panel" or in zoom that let's me change the landscape 
view the camera provides to a portrait view.  If I turn the webcam 
sideways, it rotates the image rather than changing the ratio of the 
aspect ratio.  Does anyone know a way to change the aspect ratio from 
16:9 to 9:16 or change it from 4:3 to 3:4?