Complex sentence: After the Battle of Mohács in 1526, Transylvania became part of the Kingdom of János Szapolyai which, in 1571, was transformed into the Principality of Transylvania ruled primarily by Calvinist Hungarian-speaking princes.
Split into simpler sentences: After the Battle of Mohács in 1526, Transylvania became part of the Kingdom of János Szapolyai. Later on, 1571, the kingdom was transformed into the Principality of Transylvania-which was ruled primarily by Calvinist Hungarian-speaking princes.