Virtual Camera Feed not an option?

I would like to be able to use the feed from my webcam through the software Youcam9 rather than the "real" or native feed, as Youcam9 allows greater flexibility (for example allowing me to zoom-in on my face or something else). However Zoom seems to allow me only the native feed from my webcam. Am I missing something? I've been all through Settings and don't find a solution.