.zip is an archive format using, usually, the Deflate compression method. The .gz gzip format is for single files, also using the Deflate compression method. The zlib library provides Deflate compression and decompression code for use by zip, gzip, png (which uses the zlib wrapper on deflate data), and many other applications. - Mark Adler (SO)

• Zip Files History
• History of Lossless Data Compression Algorithms

lib

• zlib-ng - zlib data compression library for the next generation systems
  • The motivation for this fork was seeing several 3rd party contributions with new optimizations not getting implemented into the official zlib repository.
• miniz - a lossless, high performance data compression library in a single source file that implements the zlib (RFC 1950) and Deflate (RFC 1951) compressed data format specification standards. It supports the most commonly used functions exported by the zlib library, but is a completely independent implementation so zlib’s licensing requirements do not apply.