Identify the letter-cluster that does not belong to the following series.
BYO, DZQ, HBU, NEZ
Each term's first letter changes at a difference of 2, 4, and 6.
The second letter is changing at a difference of 1, 2, and 3.
The third letter is changing at a difference of 2, 4, and 5. But it has to be 2, 4, 6.
So, the last term is not in the correct order.