Problem compiling codes using codesourcery cross compiler.

Hi, I have installed Angstrom to my BeagleBoard and downloaded the arm-
linux cross compiler from codesourcery. I need to compile a project
name Microgear (downloaded from internet), however I got the following
error during compiling: Cannot find zlib.h.

I found zlib.h from the directry /usr/include folder. Hence I tried to
call zlib.h from this folder but when I recompile again, it says

"undefined reference to `gzopen'",
"undefined reference to `gzclose'",
"undefined reference to `gzwrite'" and
"undefined reference to `gzflush'"

I did set the configure host to the arm-linux compiler. May I know
what went wrong here? If I didn't use the cross compiler, I can make
the same project without any error. However I need the cross compiler
for it to run on BeagleBoard.

Thank you so much in advance.