For those of you looking for some additional zoom-in on your webcam, you might want to try simply adding some reading glasses. This is probably the cheapest way to get a zoom webcam if you have some old reading glasses around.
The focus was a problem for closeups, so I cut a pair of dollar-store +3 reading glasses in half and wrapped the earpiece around the back of the webcam. With a little encouragement it clips the lens over the flat part of the webcam’s orb where the lens peeks out. Perfect.