I assume you're aware of this, but just in case you aren't, zvbi requires "lots" of patches to get to even compile in mingw cross compilation (targeting windows):
https://github.com/videolan/vlc/tree/master/contrib/src/zvbi lists all the patches they use.
Also even then only building the library works, if you try and build the executables, you get this:
libtool: link: i686-w64-mingw32-gcc -DPTW32_STATIC_LIB -o zvbi-ntsc-cc.exe ntsc-cc.o ../src/.libs/libzvbi.a -lpthread /home/rogerdpack/dev/ffmpeg-windows-build-helpers/sandbox/mingw-w64-i686/i686-w64-mingw32/lib/libiconv.a
../src/.libs/libzvbi.a(io.o):io.c:(.text+0xb9c): undefined reference to
../src/.libs/libzvbi.a(io.o):io.c:(.text+0xc9f): undefined reference tomunmap’
collect2: error: ld returned 1