FRIEND : FPIBNZ :: PATRON : ?

FRIEND : FPIBNZ

Follows a pattern that,

F - F

R- second letter to left of R i.e, P

I - I

E - Third letter to left of E i.e, B

N - N

D - Fourth letter to left of D i.e, Z

Similarly, for PATRON 

P - P

A -  second letter to left of A i.e, Y

T - T

R - Third letter to left of R i.e, O

O - O

N - Fourth letter to left of N i.e, J

PATRON : PYTOOJ

Therefore, FRIEND : FPIBNZ :: PATRON : PYTOOJ