Ok, so I found all the emulators in Retropie Setup under Manage Packages and I installed Frotz which I was immediately able to play Zork on. I still wanted to figure out my original problem though, so I changed my emulator to CapriceRPI (I was actually on lr-caprice32 before). But now, whenever I enter CAT or any command to play the game, it says:
Drive A: disc missing
So my original problem is still unsolved but at least I can now play Zork and I know how to mess with the emulators.