From IFWiki

e-ZIL is the Emacs Z-Machine Interface Language, which is an authoring system which was under development by Marc Simpson. However, this project is now officially dead.

Here is the intro from its homepage:

e-ZIL offers a Lisp interface and interaction layer for the composition of Interactive Fiction, targeted at the popular Z-Machine platform.

Designed to run from within Emacs, the user is offered an integrated development environment, composition being available through either compound Lisp expressions and/or a more interactive, reactive layer.