Almost every one as far as I know where based on the info-zip code by Mark Adler and Jean-loup Gailly. That was used as the base at the time for zip/unzip in

Almost every one as far as I know where based on the info-zip code by Mark Adler and Jean-loup Gailly. That was used as the base at the time for zip/unzip in linux, winzip, and gzip ultimately.