The letter cluster DRB should come in place of the question mark.
The series consists of 3-letter groups: PZN, MXJ, JVF, GTB, ?
Each position follows its own distinct pattern:
1st Letter (P → M → J → G → ?): Moves backwards by 3 letters each time.
P (-3) = M
M (-3) = J
J (-3) = G
G (-3) = D
2nd Letter (Z → X → V → T → ?): Moves backwards by 2 letters each time.
Z (-2) = X
X (-2) = V
V (-2) = T
T (-2) = R
3rd Letter (N → J → F → B → ?): Moves backwards by 4 letters each time.
Combining the results gives DRB.