Upload speed drops when multiple users zoom

Normally I get good download/upload speed test results even with regular internet use (not just idle line). 180-200Mbps Down. 11Mbps Up. My modem router is a Netgear C7000v2.

But I noticed that if one of two members of the household are on zoom/video calls then the upload speed drops dramatically - down to just 1 - 2Mbps. Download still remains good though at 180+Mbps.

Is this normal ? I thought upload speeds hold pretty static even with multiple users ? Or is my wifi not able to keep up ? Its a pretty new modern gateway. What might be the issue ?