All the OEM E36 vert tops have the zip out back window. The emiata window is a really good buy if you're on a budget.
To verify you've got an zip out, look at the back window on the inside, you may have to pull back the cloth a bit to see the zipper. You can't see it from the outside.
2006 Z4 3.0si Sport Package (But I'll still hang with my "homies" in the E36 forum)