Guest Join into Teams (Poly X series)

Hi

Ive seen some toher posts re this...Our X series are all on latests firmware etc...

Zoom tenant is correctly setup to support/enable guest join from Zoom into a Teams meeting.

However were still experiencing lower quality video....

I wanted to ask if there are any specific/additonal ports required by Zoom? 

I had assumed the Zoom Room connects normally to the cloud service and its there (Zoom cloud) that bridges directly with Teams therefor nothing extra required on the LAN or WAN  ?

In which case does Zoom themselves throttle or restrict the Teams sessions ?