Complex sentence: In the first half of 1527, Ferdinand was outside of Hungary, preparing to fight Zapolya, who was during that time sending armies after Jovan Nenad, wishing to destroy him before Ferdinand could come to Hungary.
Split into simpler sentences: In the first half of 1527, Ferdinand was outside of Hungary, preparing to fight Zapolya. During that time, Zapolya sent armies after Jovan Nenad, wishing to destroy him before Ferdinand could return to Hungary.