Complete the given series.
CBZ, FEW, IHT, ___

Let's analyze the pattern for each letter in the clusters:
1. First Letter: $\text{C (+3)}\to \text{F (+3)}\to \text{I (+3)}\to \text{L}$
2. Second Letter: $\text{B (+3)}\to \text{E (+3)}\to \text{H (+3)}\to \text{K}$
3. Third Letter: $\text{Z (-3)}\to \text{W (-3)}\to \text{T (-3)}\to \text{Q}$

Combining these letters, the missing cluster is LKQ.