Dan,

Please consider ZStandard, LZ4 and LZMA2 as compression options. All have friendly licenses. At a minimum, ZStandard is faster and more effective than zlib. LZ4 is the fastest and smallest memory footprint, and LZMA2 will give you the best compression, great for a smart contract that compresses once and decompresses many times.

Having a compression type in the smart contract data structure would at least allow adding new compression types in the future.