Zoom for iPad video

I’m trying to screen record a zoom session with my friend to post on instagram reels and I need it to be in Portrait mode (vertical) while the camera stays in landscape (horizontal) so that the two horizontal frames will stack vertically. But I can’t figure out how to change the video orientation without the stacks changing orientation too. I tried locking the orientation but that locks everything. I want to hold my iPad vertical but have my camera rotate to landscape. Please help I’m so frustrated.