Jake, You are asking a challenging question, I think! Many probably don't host with Zeus, so no one knows for sure. Zeus is not a 'commonly' used platform for Moodle hosting. Me, am just here to 'begin the question game' ...
There is a previous discussion concerning Zeus:
https://moodle.org/mod/forum/discuss.php?d=131149
in which a user does state they have been successful with 1.9.x but 2.x has been problematic.
Error 500's leave much to investigate and with no other information, there's not much to go on - thus not much to 'discuss' ... however ...
In your PHP info (and you say Zeus doesn't support .htaccess tweaks) there is no php tweak ability. Loaded config for php is:
/magma/hosting/magma/software/tools/etc/php-5/php.ini
something you cannot edit/tweak.
You say, however, that you had a Moodle running but that the hosting provider changed something and now you cannot run/install a 2.3.x.
Hmmmmm ... would think your first point of contact would be your provider. Have located their knowledgebase which I must say is not that helpful. If you plan to have a large Moodle presence you might run into problems with DB connections:
http://magmahost.com/my/knowledgebase.php?action=displaycat&catid=10
Without allowing .htaccess tweaks to php I see by the phpinfo that the max_execution time is already set very liberally (20000), but then again, it's a shared host. Wonder how many customers are on the same machine?
Did you try Magmahost support and they pointed you to here?
On thing you could try ... make a copy of config-dist.php renaming it to config.php. Edit and fill in the values for variables. Those values might need to be acquired from hosting provider, but this much is shown in your php.info:
document root is: /magma/users/u76/prodirct/public_html
Moodle does prefer to have it's data directory NOT in document root but it must be readable/writable to the apache user. On a CentOS Linux server that is usually up one level from document root ... so taking your document root path above:
/magma/users/u76/prodirct/moodledata
Is the moodledata directory created? (installation will not create it for you). And does it have read/write permissions by the apache user?
Some remotely hosted systems won't let Apache read/write to anything outside of document root, however.
I see that moodle is installed at the root of your document root.
So that's one variable to remember: http://professionaldirector.com
See that installation process begining is available but hangs at:
http://professionaldirector.com/admin/index.php?lang=en&agreelicense=1
The error shown:
The page you requested could not be served. This could happen for a variety of reasons, including:
A CGI script failed to produce any output.
The server is incorrectly configured.
The server encountered a critical error.
See the server API is CGI/FastCGI - gateway interface.
Just guessing but with a setting of 50M memory limit, I'd say you're gonna have a tough time running Moodle 2 anything.
Basically, think it's apache conf but since don't know about Zeus ... ????
But ... if you'd care to know more about Zeus ... think this might help (and you might be able to use it when chatting with your hosting provider):
http://support.zeus.com/zws/integration/2005/11/08/php_info
There is a section on Tuning FastCGI/PHP and the Operating System
To be honest ... from what I read about Zeus, provider needed to upgrade Zeus ... which comes with pre-compiled php binary. The suggestion that Moodle software was at fault and you needed to upgrade sounds/smells like smoke to me!
Have you considered shopping around for another hosting provider to run Moodle 2?
'spirit of sharing', Ken