How does zoom compress the video so well?

Whenever I have to edit a recorded video and re-render, my file sizes are often 10x larger than the original mp4 file produced by zoom.

Anyone have any idea how to get the same quality in that same footprint?

I'm using CyberLink\PowerDirector\16.0

Perhaps that's the problem?

H264 1920x1080 30 fps (16 Mbps)

I get a 3.5 GB file, as compared to the original zoom mp4 file size of ~300 KB