Attempting to install the zlib-devel on mac os x mavericks with homebrew doesn't work:
brew install zlib-devel
Error: No available formula for zlib-devel
Searching taps...
This install
brew install zlib
works fine though.
Just run in the command line:
xcode-select --install
In OS X 10.9+, the command line developer tools are now installed on demand. So after running this also zlib and zlib-devel should be available (no need for brew install zlib...)