zlib
Visual Studio (nmake)
Open a Visual Studio command prompt
Change directory to the zlib folder
Follow the instructions in win32/Makefile.msc
opus & opusenc
Visual Studio 2019
It is possible to build with the v141_xp platform toolset. You may need to use an older version of Visual Studio 2019. You may need the VS 2015-2019 redistributable. Furthermore, when targeting Windows XP, you may need the particular redistributable version described here.
Build steps:
git clone opus and libopusenc
Open Visual Studio project file
Change platform toolset to v141_xp (if Windows XP support is desired)
Change configuration to ReleaseDLL