/usr/bin/ld: cannot find -lz
collect2: ld returned 1 exit status

[root@localhost trunk]# find / -name libz*
/lib64/libz.so.1
/lib64/libz.so.1.2.3
/lib/libz.so.1
/lib/libz.so.1.2.3
/usr/lib64/libz.so
/usr/lib64/purple-2/libzephyr.so
/usr/lib64/libzip.so.1.0.0
/usr/lib64/libzip.so.1

[root@localhost trunk]# ldconfig -v | grep -v ^$'t'
/usr/lib64/ctapi:
/usr/lib64/mysql:
/usr/lib64/tcl8.5/tclx8.4:
/usr/lib64/xulrunner-2:
/lib:
/lib64:
/usr/lib:
/usr/lib64:
/lib/i686: (hwcap: 0x0008000000000000)
/lib64/tls: (hwcap: 0x8000000000000000)
/usr/lib64/tls: (hwcap: 0x8000000000000000)
/usr/lib64/sse2: (hwcap: 0x0000000004000000)
/lib/i686/nosegneg: (hwcap: 0x0028000000000000)

[root@localhost trunk]# yum list zlib-devel
 Installed Packages
 zlib-devel.i686     1.2.3-27.el6             @sl
 zlib-devel.x86_64   1.2.3-27.el6             @sl

[root@localhost trunk]# ls -l /lib/libz.so*
lrwxrwxrwx. 1 root root    18 Feb 23 22:58 /lib/libz.so -> /usr/lib64/libz.so
lrwxrwxrwx. 1 root root    13 Feb 18 12:06 /lib/libz.so.1 -> libz.so.1.2.3
-rwxr-xr-x. 1 root root 75332 Dec 10  2011 /lib/libz.so.1.2.3

yum list installed | grep zlib

# rpm -ql zlib-devel
/usr/include/zconf.h
/usr/include/zlib.h
/usr/lib64/libz.so                  <---- the symlink I mentioned
/usr/lib64/pkgconfig/zlib.pc
/usr/share/doc/zlib-devel-1.2.3
/usr/share/doc/zlib-devel-1.2.3/README
/usr/share/doc/zlib-devel-1.2.3/algorithm.txt
/usr/share/doc/zlib-devel-1.2.3/example.c
/usr/share/doc/zlib-devel-1.2.3/minigzip.c
/usr/share/man/man3/zlib.3.gz
# rpm -ql zlib-devel.i686
/usr/include/zconf.h
/usr/include/zlib.h
/usr/lib/libz.so                    <---- the symlink I mentioned
/usr/lib/pkgconfig/zlib.pc
/usr/share/doc/zlib-devel-1.2.3
/usr/share/doc/zlib-devel-1.2.3/README
/usr/share/doc/zlib-devel-1.2.3/algorithm.txt
/usr/share/doc/zlib-devel-1.2.3/example.c
/usr/share/doc/zlib-devel-1.2.3/minigzip.c
/usr/share/man/man3/zlib.3.gz

# ls /usr/lib/libz.so -lhA
lrwxrwxrwx. 1 root root 23 Feb 23 20:32 /usr/lib/libz.so -> ../../lib/libz.so.1.2.3
# ls /usr/lib64/libz.so -lhA
lrwxrwxrwx. 1 root root 25 Feb 23 20:24 /usr/lib64/libz.so -> ../../lib64/libz.so.1.2.3