This small extension wraps zlib to offer simple compression/decompression functions for GameMaker: Studio (1, 2) games.
Note: In current versions of GameMaker Studio 2 you can use built-in functions buffer_compress and buffer_decompress for the same purpose.
It allows to deflate/inflate sections of buffers, including support for compression levels and error handling.
A manual is available online.
Source code is available at BitBucket.