Zooming in and out in Detail for iOS / iPadOS can happen before or after a recording (not during), and works for both the selfie and rear camera.
Here is how to do that:
You can do this before and after recording
In your open project, tap Layout (bottom menu)
Now using two fingers, pinch and hold, open your fingers to zoom in and close them to zoom out.
Note: when zooming out the video layer will get smaller if you zoom out further than the background canvas size