Check this out guys,

NI is releasing the brand new design X1 and the functions are similar to Z2,
the new X1 can control play/stop every decks,
has Flux mode as Z2.
has 4 hot-ques each decks as Z2

so looks like Z2+F1 combination isn't necessary or useless..
X1 is $200 vs Z2 is $799 (no more $599 discounted price)

The main feature of Z2 was hotques and flux mode for me..