Z X _ T R _ N L J _ F D_

The given letter series in below pattern.
Z (-2) → X (-2) →V
T (-2) → R (-2) → P
Using the same pattern, we will get complete letter series.
N (-2) → L (-2) → J (-2) → H
F (-2) → D (-2) → B
Thus , V P H B is required answer .