Complex sentence: The Piaggio P.XI engines were however too weak for the aircraft, so instead, they used two Piaggio P.XII RC.35s, which could develop 1,119 kW (1,500 hp) at take-off.
Split into simpler sentences: The Piaggio P.XI engines were too weak for the aircraft, so instead, two Piaggio P.XII RC.35 were used. These could develop 1,119 kW (1,500 hp) at take-off.