[root@servergis ~]# yum install postgis2_92
--> Finished Dependency Resolution
Error: Package: gdal-libs-1.9.2-5.rhel6.x86_64 (pgdg92)
           Requires: libz.so.1(ZLIB_1.2.0)(64bit)
Error: Package: gdal-libs-1.9.2-5.rhel6.x86_64 (pgdg92)
           Requires: libjpeg.so.62(LIBJPEG_6.2)(64bit)
Error: Package: postgis2_92-2.1.5-1.rhel6.x86_64 (pgdg92)
           Requires: libjson-c.so.2()(64bit)
Error: Package: postgis2_92-client-2.1.5-1.rhel6.x86_64 (pgdg92)
           Requires: libjson-c.so.2()(64bit)
 You could try using --skip-broken to work around the problem
 You could try running: rpm -Va --nofiles --nodigest

----

[root@servergis ~]# yum provides libz.so.1
Loaded plugins: refresh-packagekit, security
zlib-1.2.3-27.el6.i686 : The zlib compression and decompression library
Repo        : rhel-rh63x64
Matched from:
Other       : libz.so.1



zlib-1.2.3-27.el6.i686 : The zlib compression and decompression library
Repo        : installed
Matched from:
Other       : Provides-match: libz.so.1

----

[root@servergis ~]# yum info zlib
Loaded plugins: refresh-packagekit, security
Installed Packages
Name        : zlib
Arch        : i686
Version     : 1.2.3
Release     : 27.el6
Size        : 136 k
Repo        : installed
From repo   : rhel-rh63x64
Summary     : The zlib compression and decompression library
URL         : http://www.gzip.org/zlib/
License     : zlib and Boost
Description : Zlib is a general-purpose, patent-free, lossless data compression
            : library which is used by many different programs.

Name        : zlib
Arch        : x86_64
Version     : 1.2.3
Release     : 27.el6
Size        : 149 k
Repo        : installed
From repo   : rhel-rh63x64
Summary     : The zlib compression and decompression library
URL         : http://www.gzip.org/zlib/
License     : zlib and Boost
Description : Zlib is a general-purpose, patent-free, lossless data compression
            : library which is used by many different programs.