I found the ZILF download here: https://bitbucket.org/jmcgrew/zilf/wiki/Home
I have found this Infocom manual very handy: https://archive.org/details/Learning_ZIL_Steven_Eric_Meretzky_1995/page/n11/mode...
More information and resources: https://vaporware.atlassian.net/wiki/spaces/ZC/pages/199819268/Getting+Started