If your server is remotely hosted and on a shared system you may not have access levels enough to add a php extension system wide. You'll have to contact provider support with the issue and ask them to set your stuff up with that extension.
If you have command line access the following will show if the required extensions are indeed loaded:
[root@sos php.d]# php -m |grep zip
zip
[root@sos php.d]# php -m |grep zlib
zlib
They will also be listed in a phpinfo.php page.
IF your server is standalone ... ie, you are the only customer ... and it's a 'typical/stock' install of CentOS, the the php.ini is in /etc/
The loading of extensions, however, on a CentOS standalone, there is a /etc/php.d/ directory. In there one will see multiple .ini files all related to php extensions. If php54-zip and php54-zlib extensions are indeed installed one will see a zip.ini file and contained therein are these two lines:
; Enable zip extension module
extension=zip.so
If you add that file, for apache to load the extension, you'll have to restart the apache service.
IF apache error logs complain or apache won't launch then undo the zip.ini file.
If file is not there, that's strange ... something is not right!
Are you sure php54-commons was installed?
'spirit of sharing', Ken