How to Seamlessly Add Zoom to QuickTime Videos Using iMovie

I want to make a video of my Mac screen with seamless screen-zooming. I have been using QuickTime Player to record the screen, and can zoom the screen during the recording, except that QuickTime continues to record the 
full screen. I would like to avoid video segments if possible. Is there a solution to this problem?

QuickTime Player is great for doing short screen captures when you need only limited editing capabilities, but to do more professional screen captures with screen zooming and other niceties, you’ll want to turn to a screen-capture application like Screen Flow