Zork was implemented in a dialect of LISP called "MDL" aka "MIT Design Language" aka "Muddle" [1], which ZIL was based on.
Here's the original MDL source code, that people should study in school, which reads like an epic poem about heroic adventures such as Beowulf! [2]
I'd love for some academic egghead literary critic type to deconstruct [3] the Zork MDL source code, like Chaim Gingold deconstructed SimCity for their PhD thesis. [4]