So i testdrive a ZL1 last weekend:
Interior: not that bad, never a M3 interior, but good for a Muscel-Car. the windows are very small, like a chopped feeling in it.
but the seats are not good, i think i'm too small for it...
Power: car pulls like hell, but i just pull it to 4000rpm, cause it was a new car.
Brake: Brembo BBK.... great!
Handling/Suspension: well, it's good, but you feel the heavy weight of the car. really bad are the steering. it feels sooo indirect! horrible! a Hyundai have the better steering than this car!
over all, i will keep my M3. it's way the better car, also a ZL1 isnt cheap here in Switzerland.
the ZL1 isnt a bad car, but if you want a great balance car like the M3, you need to put al dot of $$$ in it.