Four letter-clusters have been given, out of which three are alike in some manner and one is different. Select the letter-cluster that is different.

ZTOL JDYU OIDZ AUPL

ZTOL

ZTOL ⇒ Z →(-6)→ D→(-5) → O →(-3) → L JDYU ⇒ J →(-6)→ D→(-5) → Y →(-4)→U OIDZ ⇒ O →(-6)→ I→(-5) → D →(-4)→Z AUPL ⇒ A →(-6)→ U →(-5) → P →(-4)→ L