Analyze the pattern of letter changes in each group and find the missing group that completes the series.
TZC, WVH, ZRM, ____, FJW, IFB

Let's examine the positions of the letters in each position of the triplets:
1. First Letter: $\text{T, W, Z, ?, F, I}$
* $\text{T}(20)\stackrel{+3}{\to }\text{W}(23)$
* $\text{W}(23)\stackrel{+3}{\to }\text{Z}(26)$
* $\text{Z}(26)\stackrel{+3}{\to }\text{C}(3)$
* $\text{C}(3)\stackrel{+3}{\to }\text{F}(6)$
* $\text{F}(6)\stackrel{+3}{\to }\text{I}(9)$
The first letter increases by $+3$. So, the missing first letter is $\text{C}$.

2. Second Letter: $\text{Z, V, R, ?, J, F}$
* $\text{Z}(26)\stackrel{-4}{\to }\text{V}(22)$
* $\text{V}(22)\stackrel{-4}{\to }\text{R}(18)$
* $\text{R}(18)\stackrel{-4}{\to }\text{N}(14)$
* $\text{N}(14)\stackrel{-4}{\to }\text{J}(10)$
* $\text{J}(10)\stackrel{-4}{\to }\text{F}(6)$
The second letter decreases by $-4$. So, the missing second letter is $\text{N}$.

3. Third Letter: $\text{C, H, M, ?, W, B}$
* $\text{C}(3)\stackrel{+5}{\to }\text{H}(8)$
* $\text{H}(8)\stackrel{+5}{\to }\text{M}(13)$
* $\text{M}(13)\stackrel{+5}{\to }\text{R}(18)$
* $\text{R}(18)\stackrel{+5}{\to }\text{W}(23)$
* $\text{W}(23)\stackrel{+5}{\to }\text{B}(28\equiv 2)$
The third letter increases by $+5$. So, the missing third letter is $\text{R}$.

Combining them, the missing group is $\text{CNR}$.