What is the next letter in series AZEBIYO?

This is a tricky one! There's no immediately obvious pattern. Here's why it's difficult and some possibilities:

* No Consistent Pattern: There's no simple alphabetical or numerical pattern that jumps out.

* Possible Code or Cipher: It could be a coded message or a cipher, but without more clues, it's hard to decipher.

* Multiple Solutions: There might be multiple letters that could fit depending on the hidden rule.

Without more information, it's impossible to definitively say what the next letter is.

Let me know if there's any other context or clues you can provide!