Part of a series of similar puzzles - the answer to one will give you the type of thinking required for the others.
What's the next letter in this series? What's the relationship?
L K Z R A O T E L A I D L N A S Y A E D A
The next letter in the sequence is:
Because the letters are:
The second letter of the abbreviations for U.S. States, in alphabetical order:
Alabama > AL > L
Alaska > AK > K
Arizona > AZ > Z
The last state in the list is Massachusetts, so the next is Michigan
Michigan > MI > I