Complex sentence: At the peak of his power, Jovan Nenad crowned himself emperor though he was little more than a brigand leader siding first with the Zapolyai and then with the Habsburg pretender as circumstances allowed.
Split into simpler sentences: At the peak of his power, Jovan Nenad crowned himself emperor more than a brigand. He first sided with the Zapolyai and then with the Habsburg pretender as circumstances allowed.