I'm running POP OS at the moment (until I get Zorin to install). However, I also have a 4K monitor and scaling generally and fractional scaling specifically (in POP OS) have been a problem for me.
What I've done is disable fractional scaling and use Gnome Tweaks to scale the font size. Generally this works, but some apps don't space properly for increased font size (Audacity for example).
In the live demo of Zorin, I tried increasing the font sizes from its settings panel (not using Gnome Tweaks). This seemed to work surprisingly well. I would try this first.