Complex sentence: The Boeing B-29 Superfortress was a development of the Fortress, but a larger design with four Wright R-3350 Duplex-Cyclone engines of much greater power, enabling it to fly higher, faster, further and with a bigger bomb load.
Split into simpler sentences: The Boeing B-29 Superfortress was a development of the Fortress, but with four Wright R-3350 Duplex-Cyclone engines of much greater power. This enabled it to fly higher, faster, further and with a bigger bomb load.