My goal is to inject packet loss into a Zoom call to see what happens, but I'm not sure about the setup.
With two laptops on my network (each connected to a switch) and Connection Emulator active on one of them, I can create packet loss between the two computers, yet the outgoing Zoom stream to the internet is unaffected. Do I need to connect my "Zoom" laptop to the Emulator laptop and pass through the Zoom call, or can both be connected to the switch and adjust outgoing Zoom traffic?
If, as you describe, you have Zoom on one laptop and Connection Emulator on the other, it's not going work. Zoom's network packets will travel directly to the Internet and back unaffected. The laptop that has Connection Emulator installed will never receive Zoom packets.
The simplest way to make it work is to install both Zoom and Connection Emulator on the same computer. In this case, all or some (if you set a filter) traffic will be intercepted and packet loss will take place. You can test it by simply running a ping to a web-site or router and see how the output changes when you introduce packet loss.
Another (harder) way would be to turn one laptop into a bridge or router and direct Zoom laptop traffic via it, but this will likely need two NICs and the setup is more complex: