How to increase recording quality

Since the question lacks detail about what you ARE doing it is difficult to answer such a general question. There are many ways to improve recording quality. If you are just using a webcam expect the image to be 640 x 360 and the recording to be the same. If you use screen share with HD turned on in the web portal and in the client and you have at least one participant with the Zoom window set to full screen you can get 1280 x 720 for the recording; however the webcam will still be 640 x 360. If you screen share an HD camera then the recording and camera will be 720P.  There are still dozens of other ways to improve the recording including not using Zoom to record. In general most users will get 720P at best in a Zoom recording.