Poor video quality when sending OBS Virtual Camera to Zoom

I’m trying to stream a Zoom meeting from one PC using another PC with OBS Studio.

The video input signal is excellent, and the recording made directly in OBS is Full HD. However, when I send the video from OBS through Zoom, the participants receive a very low-resolution image.

Interestingly, if I stream directly from my PC (without going through OBS), the video quality looks much better.

Could anyone explain why this might be happening?

Is there any difference in video resolution depending on the Zoom plan?

Thanks in advance.