Have you actually driven either car?

Ref your comments:

 - Nope, all production TVRs are now straight sixes

 - All production TVRs are front engined

 - The Z3M weighs 1350kg, the TVR 350c weights 1100kg.  Quite clearly there is a difference, but the Z3M doesn't weight 1500kg

So on specs, you don't appear to be doing so well.

One of my friends has a Tuscan S, sounds like an angry demon with PMT, completely awesome.  IMO the Z3M is simply different.