Zipping and unzipping files in fennel has always given me headaches.
LuaZip, the default lua-zip available in Apt only allows you to read files, not write them.
Brimworks has a lua-zip library (my goto) that reads and writes, but has compatibility issue with emscripten in some browsers / operating systems.
This weekend I wrote my own minimal wrapper around lua-zlib in fennel that lets you read a zip file directly into a table of strings and vice versa.