Zynga’s aggressive development on its private cloud infrastructure, zCloud, shows us just how close the developer is to hosting an independent games platform.

Zynga started sharing more details on its cloud service as of yesterday during its Q4 earnings call, stating that about 80% of its games catalog now runs on zCloud instead of on public clouds. A blog post and infographic released today further illustrate how far the service has come in the last 12 months (click on the image to see a larger version of the infographic).

It’s significant because it means Zynga is almost ready to release its ZLive platform. For two years now, we’ve heard rumors and rough details around what ZLive — or Zynga Direct — is really supposed to be. Near as we’ve been able to tell, it falls somewhere between a fan network and a mobile social games portal built on deep Facebook integration. As early as October 2011, we knew that ZLive was capable of hosting some of its existing social games. Now that Zynga is sharing how far along zCloud has come in the last year, we know that Zynga is planning on hosting all of its games, plus some yet to be released or announced.

In its blog post, Zynga claims that zCloud is able to support more scale, efficiency and power than anything the developer experienced with public clouds through Amazon Web Services (AWS). In mid to late 2011, the developer began launching its games directly within the service instead of starting them off AWS. Mobile game CityVille Hometown was the first title onto zCloud; CastleVille followed some months later, testing the limits of infrastructure with high production values and rapid traffic growth. Zynga CTO of Infrastructure Allan Leinwand tells Inside Social Games that zCloud is already capable of supporting cross platform games for web and mobile — like Words With Friends.

The next step, then, is expanding beyond Zynga’s existing games catalog.

While Zynga certainly plans to launch more of its own IP on its own cloud and eventually on its own platform, we could potentially see Zynga publish other developers’ games on ZLive or some games portal extension thereof. Zynga hasn’t done very much with publishing as yet — beyond hiring Sony’s Rob Dyer to oversee the department and announcing a licensed Slingo game for Facebook as of this morning — but if the developer had an infrastructure capable of doing even more than what Facebook does for games, it’s not hard to imagine that Zynga would court other developers to come launch games on its service. It would go a long way toward decreasing Zynga’s dependence on Facebook.