I believe the CTS-V uses the 1.9L TVS blower vs the ZR-1 using the 2.3L TVS blower.
I'm not sure exactly of all the differences, but I know they have some differences with the supercharger, I also thought a different size pulley outputting less boost, and different intercooler. I know they also have different internals, I think rods/pistons maybe... It is a slightly "weaker" engine, but basically the same... There are several cts-v's online, youtube, etc... that have anywhere from stock hp to 1000 hp, most claim just some basic mods(intake, exhaust, tune, pulley...), I would think a few grand...