I don't know if this is of any interest to you guys, but I thought maybe someone might find this information useful or interesting.
After many hours of struggeling with Zoom, virtualcam and NDI, I found a way to broadcast my OBS output without any tools directly to Zoom in cristal clear HD. The solution is quite simple, yet efficient. But before I go there: Zoom seems to use two different algorithms/codecs. One for webcam feeds and one for the sharing feature. The video compression algorithm doesn't work well with non-regular webcam feeds, that's why the quality is really poor. It's not supposed to work with that information. The compression algorithm for the sharing feature on the other hand is a whole different story. It seems to be designed for transfering regular display content, which makes totally sense. This is at least a strong guess of mine after hours of trying to get it to work properly.
The solution: I use OBS regularly without virtualcam or NDI. OBS has a neat feature, a fullscreen preview... I simply use Zoom's sharing feature to broadcast my OBS preview screen and voilà, cristal clear HD video transfer, lag free. No patch, no third party tools, no nothing needed. Plus, I have total control of my OBS output as usual.