Error while installing Phusion Passenger for dolls

I am setting up Puppet-master version (3.7.3) on RHEL6.3 x64 where in one step I need to install Phusion Passenger.

(ref: https://docs.puppetlabs.com/guides/passenger.html)

      

        
        
        
      

    

But during

step "gem install rack passenger" I am facing the problem below:

ERROR:  Loading command: install (LoadError)
        cannot load such file -- zlib
ERROR:  While executing gem ... (NoMethodError)
    undefined method `invoke_with_build_args' for nil:NilClass

      

        
        
        
      

    

I did a lot of googling and it said everywhere that the zlib library needs to be reinstalled. I reinstalled a thousand times but no luck.

Then it felt like I should install the passenger directly from the official repo mentioned below:

https://www.phusionpassenger.com/documentation/Users%20guide%20Apache.html

      

        
        
        
      

    

But at the stage yum install mod_passenger

I ran into the problem below:

---> Package rubygem-daemon_controller.noarch 0:1.0.0-1.1.el6 will be installed
---> Package rubygem-passenger-native-libs.x86_64 1:3.0.19-1.el6_1.8.7.352 will be installed
--> Processing Dependency: ruby = 1.8.7.352 for package: 1:rubygem-passenger-native-libs-3.0.19-1.el6_1.8.7.352.x86_64
--> Finished Dependency Resolution
Error: Package: 1:rubygem-passenger-native-libs-3.0.19-1.el6_1.8.7.352.x86_64 (passenger)
           Requires: ruby = 1.8.7.352
           Installed: ruby-1.8.7.374-3.el6_6.x86_64 (@rhel-6-server-rpms)
               ruby = 1.8.7.374-3.el6_6
       Available: ruby-1.8.7.299-4.el6.x86_64 (rhel-6-server-rpms)
           ruby = 1.8.7.299-4.el6
       Available: ruby-1.8.7.299-5.el6_0.1.x86_64 (rhel-6-server-rpms)
           ruby = 1.8.7.299-5.el6_0.1
       Available: ruby-1.8.7.299-7.el6.x86_64 (rhel-6-server-rpms)
           ruby = 1.8.7.299-7.el6
       Available: ruby-1.8.7.299-7.el6_1.1.x86_64 (rhel-6-server-rpms)
           ruby = 1.8.7.299-7.el6_1.1
       Available: ruby-1.8.7.352-3.el6.x86_64 (rhel-6-server-rpms)
           ruby = 1.8.7.352-3.el6
       Available: ruby-1.8.7.352-4.el6_2.x86_64 (rhel-6-server-rpms)
           ruby = 1.8.7.352-4.el6_2
       Available: ruby-1.8.7.352-7.el6_2.x86_64 (rhel-6-server-rpms)

      

        
        
        
      

    

There were also a couple of dependencies like rubygem (rake)> = 0.8.1 and libev.so.4 () (64 bit), which I googled and installed using single RPMs.

Now I don't understand how to solve this. Any suggestions would be really helpful here.

Puppet -V: 3.7.3

ruby 2.1.5p273 (version 2014-11-13, revision 48405)

Gem -Version: 2.4.4

RHEL 6.3 x64

Thank!