Installing GEMS on AIX 5.3

I am trying to install rubygems-0.9.0 and I keep getting this error
message whenever i run the command ruby setup.rb,

root:/var/tmp/ruby/rubygems-0.9.0>ruby setup.rb
—> bin
<— bin
—> lib
—> lib/rbconfig
<— lib/rbconfig
—> lib/rubygems
<— lib/rubygems
<— lib
—> bin
<— bin
—> lib
—> lib/rbconfig
<— lib/rbconfig
—> lib/rubygems
<— lib/rubygems
<— lib
rm -f InstalledFiles
—> bin
mkdir -p /usr/local/bin/
install gem /usr/local/bin/
install gem_mirror /usr/local/bin/
install gem_server /usr/local/bin/
install gemlock /usr/local/bin/
install gemri /usr/local/bin/
install gemwhich /usr/local/bin/
install index_gem_repository.rb /usr/local/bin/
install update_rubygems /usr/local/bin/
<— bin
—> lib
mkdir -p /usr/local/lib/ruby/site_ruby/1.8/
install gemconfigure.rb /usr/local/lib/ruby/site_ruby/1.8/
install rubygems.rb /usr/local/lib/ruby/site_ruby/1.8/

install ubygems.rb /usr/local/lib/ruby/site_ruby/1.8/
—> lib/rbconfig
mkdir -p /usr/local/lib/ruby/site_ruby/1.8/rbconfig
install datadir.rb /usr/local/lib/ruby/site_ruby/1.8/rbconfig
<— lib/rbconfig
—> lib/rubygems
mkdir -p /usr/local/lib/ruby/site_ruby/1.8/rubygems
install builder.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install cmd_manager.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install command.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install config_file.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install custom_require.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install dependency_list.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install doc_manager.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install format.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install gem_commands.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install gem_openssl.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install gem_runner.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install incremental_fetcher.rb
/usr/local/lib/ruby/site_ruby/1.8/rubygems
install installer.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install loadpath_manager.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install old_format.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install open-uri.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install package.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install remote_installer.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install rubygems_version.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install security.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install source_index.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install specification.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install timer.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install user_interaction.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install validator.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
install version.rb /usr/local/lib/ruby/site_ruby/1.8/rubygems
<— lib/rubygems
<— lib

As of RubyGems 0.8.0, library stubs are no longer needed.
Searching $LOAD_PATH for stubs to optionally delete (may take a
while)…
…done.
No library stubs found.

/usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in
gem_original_require': no such file to load -- zlib (LoadError) from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:inrequire’
from /usr/local/lib/ruby/site_ruby/1.8/rubygems/package.rb:9
from
/usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in
gem_original_require' from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:inrequire’
from /usr/local/lib/ruby/site_ruby/1.8/rubygems/builder.rb:7
from
/usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in
gem_original_require' from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:inrequire’
from /usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:93:in
manage_gems' from /var/tmp/ruby/rubygems-0.9.0/./post-install.rb:70:ininstall_sources’
from /var/tmp/ruby/rubygems-0.9.0/./post-install.rb:81:in
try_run_hook' from setup.rb:577:inrun_hook’
from setup.rb:1315:in exec_task_traverse' from setup.rb:1168:inexec_install’
from setup.rb:887:in exec_install' from setup.rb:705:ininvoke’
from setup.rb:674:in `invoke’
from setup.rb:1352

I have ruby 1.8.5 installed correctly and I have zlib-1.1.4-2 which I
have set the path to, and zlib-devel-1.2.3-3, and I am still gettign
this error. Any ideas?