Zoom icon too large and blurry in system tray
Solution 1:
I had the same problem with Forticlient VPN and found a workaround for it: find the image in the installation directory of your application and resize it to a smaller size, e.g. using nomacs.
In my case, I resized the original icon size of 42x42 to 16x16, which was a bit too small though. It seems that 20x20 could be fine.
The above is a workaround, but at least it prevents overlapping of the top panel over fullscreen window controls.