Bit of a late reply, but...
That figure of 60 litres came from Wheels (Australia) magazine, August 2003 (they tested a Zonda C12S 7.3). Looks like they most probably are wrong, or that the C12S has a different fuel tank to the Zonda F... Read on...
Sport Auto list tank capacity for the Zonda F as 95 litres, as seen here:
http://www.supercars.net/pitlane/pics/2287958d.jpg
Entire set can be seen through the link below:
http://www.supercars.net/PitLane?vie...83550&bottom=0