As a drop-in replacement, we have plan to switch zlib with zlib-ng. See COMP: Switch to modern maintained zlib-ng fork of zlib by jamesobutler · Pull Request #6708 · Slicer/Slicer · GitHub
Instead of transitioning to fastzip (currently unmaintained), we will likely add support for GitHub - facebook/zstd: Zstandard - Fast real-time compression algorithm