Complex sentence: After Zeck is mutated, Shredder then has Stockman-Fly add white rhinoceros DNA in the second mutagen batch to have Steranko mutated for his betrayal, announcing that his animal (the rhinoceros) is apropos.
Split into simpler sentences: After Zeck is mutated, Shredder then has Stockman-Fly add rhinoceros DNA in the second mutagen batch to have Steranko mutated for his betrayal. He tells Steranko that his animal (the rhinoceros) is apropos.