Complex sentence: The neighbouring Holy Roman Empire eventually invaded Croatia in 1067 by sending the Carantanian army to occupy the northern Banate, which was probably a result of Zvonimir's close ties with Hungary, who was in a war with the empire at the time.
Split into simpler sentences: The neighbouring Holy Roman Empire invaded Croatia in 1067 by sending the Carantanian army to occupy the northern Banate. This was probably a result of Zvonimir's close ties with Hungary, who was also in a war with the empire at the time.