Error: The following directories are not writable by your user: /usr/local/share/man/man8

[program-spiritual]

sudo chown -R $(whoami) /usr/local/share/man/man8

[program-spiritual]

zlib is keg-only, which means it was not symlinked into /usr/local,
because macOS already provides this software and installing another version in
parallel can cause all kinds of trouble.

For compilers to find zlib you may need to set:

  export LDFLAGS="-L/usr/local/opt/zlib/lib"
  export CPPFLAGS="-I/usr/local/opt/zlib/include"