CC rating is the size of the combustion chamber/dome.  They have removable replaceable domes where one can change compression for elevation or fuel or type of build etc..  The term cool head leads people to believe that they cool better than a stock head but builders say the cooling is the same---perpaps they just look cool.   In any event--for the zilla one would still need to have the domes correctly modified or cut for a proper squish band clearence as you would on any factory head.   A popular modification to the cool head ( or any head) is to have it cut for 0-rings.  This eliminates the need to use expensive head gaskets and you can re use the o ring. Some say the 0-ring seals better than stock gasket as well. 

A properly set up cool head will not perform any better or worse than a properly set up stock head.