Clearly, the patterns followed by the letters are as follows :
1st letter : $Z-2 \rightarrow X, X-2 \rightarrow V, V-2 \rightarrow T,$
$T-2 \rightarrow R, R-2 \rightarrow P, P-2 \rightarrow N$
2nd letter : $A+3 \rightarrow D, D+3 \rightarrow G, G+3\rightarrow J,$
$J+3\rightarrow M, M+3\rightarrow P, P+3\rightarrow S$
The series formed by the numerals i.e. 1,2,6,21,88,445....
follows the pattern x 1 + 1, x 2 +2,x 3 + 3, x 4 + 4,x 5 + 5, .....
So, numeral in the desired term = 445 x 6 + 6 = 2676. Hence, desired term is N2676S.
Hence the answer is (a).