27 is the correct number.
I believe that the Zdeck is still being included in the first (and second) print run for the game. I haven't heard of people not receiving it as of this time.
27 is indeed the correct number, although ironically I received 33.
This thread seems to indicate that part of the 2nd printing will have the Z-deck.
A portion of the second print run will have the Z deck. There will be no changes/corrections to this run.
The reprint after this (third) may fix some of the errors. The third print run is due November time, but by this time there will be no Z deck.