For donations: https://yellowafterlife.itch.io/gamemaker-zlib
Source code: https://bitbucket.org/yal_cc/buffer_zlib
This small extension wraps zlib to offer simple compression/decompression functions for GameMaker: Studio (1, 2) games.
It allows to deflate/inflate sections of buffers, including support for compression levels and error handling.
It is free an open-source, and I am honestly surprised that no one did this yet.