as with all engines, the way to power is always the same.
a) boost it.
b) if going na, increase compression (pistons/flat valves/etc.)
c) port it.
d) (still not enough) get cams for the increased compression
e) increase more compression (pistons, etc.)
f) tune it.
no matter what the engine, it's all the same method, in that order. due to engine design, the peak power output may or may not be to your liking, but if you're sticking to zc, obviously having the biggest and latest is not a priority, so go ahead and figure out the mods that fit your taste, and most importantly, your BUDGET. :P
that's all if you already got intake, exhaust as basic mods.