The 4th term of the following alphabet series ZXYW, VTUS, RPQO, _____ , JHIG is:

Let us track the positional pattern of each letter in the 4-character clusters across the series:
1. First Letters: $Z(26)\to V(22)\to R(18)\to \mathbf{N}(14)\to J(10)$ — decreasing consistently by 4.
2. Second Letters: $X(24)\to T(20)\to P(16)\to \mathbf{L}(12)\to H(8)$ — decreasing consistently by 4.
3. Third Letters: $Y(25)\to U(21)\to Q(17)\to \mathbf{M}(13)\to I(9)$ — decreasing consistently by 4.
4. Fourth Letters: $W(23)\to S(19)\to O(15)\to \mathbf{K}(11)\to G(7)$ — decreasing consistently by 4.

Combining the calculated letters yields NLKM.