Currently, the paintings from the mod are custom entities that do not implement optimizations to vanilla paintings provided by other mods such as the Fast Paintings mod: https://www.curseforge.com/minecraft/mc-mods/fast-paintings.

I believe that Zetter should simply either add compatibility between the two mods or simply implement these fixes on its own.
One big improvement the Fast Paintings mod applies is the possibility for data-driven painting frames, which fits right into the mod's applications and provides a system for the user to create more frames (without the need for constant additions to the mod itself).