Venture Capital investors include Kleiner Perkins Caufield & Byers, Institutional Venture Partners, Foundry Group, Avalon Ventures and Union Square Ventures.
Here's a link to Zynga's roadshow presentation on RetailRoadshow: http://www.retailroadshow.com/sys/launch.asp?qv=11284801363945007&k=43589288736
Here's a link to a Forbes article about Zynga's roadshow: http://www.forbes.com/sites/tomiogeron/2011/12/02/zynga-on-roadshow-seeking-up-to-1-billion-in-ipo/