Z3 wheels are interchangeable with the Z4, and vice versa. Most of the larger standard Z4 rims are staggered sets, but they are all the same irrespective of Z4 model.
As usual always worth checking the offsets etc. I know the 108's Grimstead has will fit a Z3, as I was looking to switch wheels on my Z3/Z4 to see what the looked like.
Z3M wheels aren't a direct fit, in the same way as they aren't with non-M Z3's. Not sure I've ever seen a Z4 with them fitted, be interest to see what they looked like.