Complex sentence: The 737 MAX is based on earlier 737 designs but re-engined with more efficient CFM International LEAP-1B powerplants along with aerodynamic improvements, most notably split-tip winglets, and airframe modifications.
Split into simpler sentences: The 737 MAX is based on earlier 737 designs. However, it is re-engined with more efficient CFM International LEAP-1B powerplants, with aerodynamic improvements (most notably split-tip winglets), and with airframe modifications.