Complex sentence: As they are Leah's secret genies, they often hide when Leah's friend Zac is around, though he is mostly oblivious to all the magic and strange things that occur as a result of the twins' mistakes.
Split into simpler sentences: As they are Leah's secret genies, they must hide when Leah's friend, Zac, is around. However, he is mostly oblivious to the magic and strange things that occur as a result of the twins' mistakes.