Looks like they are going the single pipe route on the Z, unless this is just a photo-op, proof of concept prototype. I couldn't find any other official posts from them since this one in December.
I doubt a single exhaust, probably just prototyping. On the Z34 it's double. Waiting to see their final product, bet it'll sound great! FI's product is too quiet so far.
Ark makes some very nice exhaust for the Q series, I'm surprised they went with a single on the Z. Maybe this is one of two they will produce. The Ark Grip is incredibly violent sounding on the Q60, I was surprised to see they went a different route right away.
I've never really been a fan of single exit, especially on a twin turbo