I feel that downloading zlib tallballs fails frequently. At its latest commit 2322ded , downloadig 1.2.10 fails again -- the URL http://pkgs.fedoraproject.org/repo/pkgs/mingw-zlib/zlib-1.2.10.tar.gz/44d667c142d7cda120332623eab69f40/zlib-1.2.10.tar.gz is not available.

How about using zlib's github release page to server zlib tarballs? This page has a clear records of up-to-date and historical zlib tarballs. https://github.com/madler/zlib/releases