Which letter cluster will replace the question mark (?) to complete the given series?

AZBY, BYCX, CXDW, ? , EVFU

DWEV

Explanation:

AZBY, BYCX, CXDW, ? , EVFU

The logic followed here is :

A → (+1) → B → (+1) → C → (+1) → D → (+1) → E

Z → (-1) → Y → (-1) → X → (-1) → W → (-1) → V

B → (+1) → C → (+1) → D → (+1) → E → (+1) → F

Y → (-1) → X → (-1) → W → (-1) → V → (-1) → U

So, the letter-cluster that replaces the (?) to complete the series is "DWEV"