zlib-ng recently had a stable release 2.0.2. zlib-ng standalone benchmarks indicate up to multiple times faster than zlib on write and 10’s of percent faster on read. I haven’t benchmarked with HDF5, but I noticed it was simple to build HDF5 with zlib-ng.
zlib-ng may be of interest to HDF5 community as original zlib has last release in 2017, and zlib-ng incorporates improvements from some popular zlib forks since then. I simply added CMake option to Zlib:
-DZLIB_COMPAT:BOOL=on to work with HDF5.