There has been 20 diferent Zondas since the first one was produced back in 2001.
here is a list of all of them starting with from first one. The pictured ones are very limited editions (5 units, 1..):
2001 Pagani Zonda C12
2002 Pagani Zonda C12-S
2003 Pagani Zonda GR
2002 Pagani Zonda C12-S 7.3
2003 Pagani Zonda C12-S Roadster
2004 Pagani Zonda C12-S Monza
2005 Pagani Zonda F
2006 Pagani Zonda Roadster F
2008 Pagani Zonda R Prototype
2009 Pagani Zonda R
2009 Pagani Zonda Cinque
2010 Pagani Zonda Cinque Roadster
2010 Pagani Zonda PS
2011 Pagani Zonda Tricolore
2011 Pagani Zonda Uno
2011 Pagani Zonda GJ
2011 Pagani Zonda HH
2011 Pagani Zonda 750
2011 Pagani Zonda RAK
2011 Pagani Zonda Absolute