Download & unpack the latest stable release - it's near phrase "The current release is publicly available here"
Open in text editor 'win32\Makefile.msc', replace -MD to -MT
Open "VS2013 x64 Native Tools Command Prompt", set current directory to unpacked zlib dir.
Exec 'nmake -f win32/Makefile.msc'
After that you will see new files with extentions: