BTW, I am not the ZPL author, but I collect different C libraries as a personal stash of toolkits, and thought this might be interesting to other C programmers.
Might you have a write-up or link for these, and if so might you be willing to share it?
I have been using Sean Barrett's libraries [0], as well as his curated list of other people's single-header libraries [1], and, like you, I am always on the lookout for new things to add to the collection :)
I also use stb.h, and very impressed that one can put so many things together in one file. Essentially I feel C is very good at doing what most other languages are struggling at - make code running 99% of the time fast, but when it comes to that rest 1%, it takes a lot of repetitive works. I think an "essential-collection" could greatly reduce the unnecessary effort.