I included ZLib into my VS 2008 project with no problems. To include MiniZip, I included this file in my main header:
#include "../Source/Libraries/zlib-1.2.5/contrib/minizip/unzip.h"

And I added these .c files to the project:
ioapi.c
iowin32.c
mztools.c
unzip.c

(I am only concerned with unzipping files.)

When I compile the project, I get the following linker errors:
1>unzip.obj : error LNK2019: unresolved external symbol _inflateInit2_ referenced in function _unzOpenCurrentFile3
1>unzip.obj : error LNK2019: unresolved external symbol _inflate referenced in function _unzReadCurrentFile
1>unzip.obj : error LNK2019: unresolved external symbol _crc32 referenced in function _unzReadCurrentFile
1>unzip.obj : error LNK2019: unresolved external symbol _inflateEnd referenced in function _unzCloseCurrentFile

Ah, I was not including all the needed ZLib .c files. You must include the two header files, and the following: