z999z3mystorys
I've pulled the keycaps before, and they look like any other mechanical keyboard key cap in terms of mounting. I don't know if it's some sort of universal standard or not, but it looks like it'd work given what I saw of the keycaps on the z20 and the pic of the set you mentioned when I looked it up.

EVGATech_JamesL
Our keyboards as well as practically every keyboard that uses Cherry Style switch stems are compatible with keycaps that use Cherry style switch stems. 
 
Only issues some may run into is that these switches are north faced. Which means that the LED is on top which can cause some binding on Cherry Profile keycaps within the middle row. This can happen on any keyboard that has north facing switches where the LED is on top instead of the bottom of the switch. 

EVGATech_JamesL

jpace731
 

Interesting, I've never even thought to consider LED placement

This is really only an issue with Keyboard enthusiast/purists. Generally speaking I doubt you'll notice any binding issues as it mainly affects the feel and sound when you bottom out on the keys within the middle rows. For the post part you can use Any keycap set as 99.9% of them are made to fit Cherry stems and this keyboard uses the standard bottom row layout.