Just clarifying the Pagani Zonda issue, they are not powered by a motorcycle engine but a Mercedes V12. There is the Zonda C12 (6.0litre) C12S (7.0litre), and C12S 7.3.
The C12S 7.3 is the most powerful and quickest:
* 7.3L AMG V12 engine
* 6spd manual RWD
* 414Kw/555bhp
* 749Nm
* 1350kg (3.26Kg/Kw)
* 0-60mph = 3.6s
* Top Speed 220mph