ZLIB is a compression format described by RFC1950. It is also the name of the de-facto canonical C-language implementation of the format (zlib.net).

There are several native Common Lisp implementations, as well as FFI bindings:

To make it more annoying, there are at least two Common Lisp libraries also named "zlib":

In addition, CLisp has a module also called "zlib". It is part of the default "full" module linking set.