You do realise that all the lap times on that site are submitted by various people (some race drivers, some manufacturer test drivers, some journalist, some normal drivers) - and the time of one lap, on one day by one driver, does not necessarily compare to another time at the same track, with another driver - even in the same car
You only have to compare that websites info for the similarly powered (to the 35is) SLK55, and it hows the SLK55 faster in all the acceleration tests - but then all over the place at different tracks...some faster, some equal, some slower - but if you look into the details you will see some 'wet' tags next to the times, which are not tagged as such on the comparison pages.
I can't find an 'official' or 'magazine' Ring time for a 35is. - but according to SportAuto the M2 is 8m:01s, 1M is 8m:15s, Alpina Roadster S is 8m:15s.
If the 35is pulls like the M2 (
SportAuto Ring time of 8m:01s), then there's no way the Z4M will keep up on the straights...and you'd probably lose a second to 100mph just in the gear changes...and if you can't get past one under braking or through the twisties, then you're not likely to get past it trying to out drag it up a long straight either. While I agree the 35is may be quicker than the Z4M in certain parts of the Ring, I can't see it being 3 seconds faster than the M2.
I've seen very well driven Caymans pissing all over poorly-driven GT3s at the Ring, and Suzuki Swifts or Alfa 147 holding up faster cars.
Get the right driver in any car and they'll show you how quick it will really go. I've been in cars with professional drivers, seeing them changing up a gear where I'd be braking/lifting.
According to two different 'magazine' tests (Evo & SportAuto), the Z4M is a couple of seconds quicker around the Ring than an e60 M5 - but there's no way a Z4M would keep up with one of those on the straights either.
Swap the EDC with proper suspension and you may have a car which does the corners as well too!
P.S. I'd happily have a 35is.
P.P.S. I bet an 'average' driver would get closer to a professional driver's time in the 35is or Z4MR than they would in the Z4MC, as I think the coupe is just too rigid for playing and you have to out a lot more in to make it perform well.