ZLIB is a compression format described by RFC1950. It is also the name of the de-facto canonical C-language implementation of the format (http://zlib.net/).There are several native Common Lisp implementations, as well as FFI bindings:
Chipz is a decompression library for decompressing DEFLATE (RFC 1951) data such as ZLIB (RFC 1950), GZIP (RFC 1952), as well as bzip2
CL-TK provides a simple bridge to Tcl/Tk
cl-z is a set of CFFI bindings to the zlib compression library
Salza2 is a native Common Lisp compression library for creating data in the DEFLATE, ZLIB, or GZIP compression formats
To make it more annoying, there are at least two Common Lisp libraries also named "zlib":
Franz zlib (native CL)
common-lisp.net zlib (also native CL)
In addition, CLisp has a module also called "zlib". It is part of the default "full" module linking set.
A library for decompressing deflate, zlib, and gzip data
Create compressed data in the ZLIB, DEFLATE, or GZIP
Minimal bridge to Tcl/Tk
Various utilities, this is the most basic system that only introduce a small number of external dependencies.