Modified (suspension) vs stock Cayman S with equal drivers - contemporary Porsches lack a lot of negative camber adjustability from the factory so I'd speculate that a ZN6 with a well set up chassis could keep up with a stock Cayman S, depending on the track layout.
Modified (suspension) ZN6 vs modified (Suspension) Cayman S with equal drivers - yeah, you're gonna need more power.
IMHO