If we give number to each letter according to its alphabetical order we find that,
Alphabets
A
B
C
D
E
F
G
H
I
J
K
L
M
Positional value
1
2
3
4
5
6
7
8
9
10
11
12
13
Positional value
26
25
24
23
22
21
20
19
18
17
16
15
14
Alphabets
Z
Y
X
W
V
U
T
S
R
Q
P
O
N
Z - T = F i.e.26 – 20 = 6 (the positional value of F) Z - O = K i.e.26 – 15 = 11(the positional value of K) Z - K = O i.e.26 – 11 = 15 (the positional value of O) Z - I ≠ Ni.e.26 – 9 = 17 ≠ 14 (the positional value of N) Therefore, ZIN is the different one.