Find the $4^{\text{th}}$ missing term of the following alphabet series:
$$\text{ZXYW, VTUS, RPQO, \_\_\_\_\_ , JHIG}$$

Let's analyze the positioning and pattern of the first letter of each 4-letter group:
$$\text{Z}\stackrel{-4}{\to }\text{V}\stackrel{-4}{\to }\text{R}\stackrel{-4}{\to }\text{N}\stackrel{-4}{\to }\text{J}$$

The positions in reverse alphabetical order reveal a constant step of $-4$. Thus, the first letter of the missing term must be $\text{N}$.

Now look at the internal letter pattern within each individual group:

* Group 1 ($\text{ZXYW}$): $\text{Z}\stackrel{-2}{\to }\text{X}\stackrel{+1}{\to }\text{Y}\stackrel{-2}{\to }\text{W}$
* Group 2 ($\text{VTUS}$): $\text{V}\stackrel{-2}{\to }\text{T}\stackrel{+1}{\to }\text{U}\stackrel{-2}{\to }\text{S}$
* Group 3 ($\text{RPQO}$): $\text{R}\stackrel{-2}{\to }\text{P}\stackrel{+1}{\to }\text{Q}\stackrel{-2}{\to }\text{O}$

Applying the exact same internal positional shifting pattern starting with $\text{N}$:

1. First letter = $\text{N}$
2. Second letter = $\text{N}-2=\text{L}$
3. Third letter = $\text{L}+1=\text{M}$
4. Fourth letter = $\text{M}-2=\text{K}$

Combining these gives the group $\text{NLKM}$.