How do you lower zoom sensitivity with regard to keyboard shortcuts?

I use a XP Pen Artist 12 for drawing normally, but it seems like the dial on that can't let me map a combination of Ctrl + scroll wheel to it, and instead have to use the keyboard shortcuts to zoom. The problem is that that is meant more for larger incraments and not scrolling-like zooming, so is there any way to lower how much the shortcut zooms?

It would probably best if I kept using the shortcuts, so I wouldn't have to change the keys over after using Sai, but if I can change the mouse wheel zooming to just the mouse wheel then that would be good too.