Complex sentence: At the same time, the real Ajax emerge from the window and he breaks into the house, he let out a enormous roar, whom Donald momentarily believes is the triplets' disguise before spotting them.
Split into simpler sentences: At the same time, the real Ajax appears in front of the window and breaks into the house. Ajax lets out a enormous roar, but Donald momentarily assumes that Ajax is the triplets' disguise before spotting them.