I was reading up that Z3 is for use on non-clearcoated surfaces...

think ti woudl be a good idea to use on the bottom of the hood?

 

You can use either Z-2,3, or 5. The only difference in Z-3 and the others is that is has an additive in it that prevents oxidation that older single stage paints are known for. GM just does not clear under the hood for some reason, any of the polishes will help it however...........