Complex sentence: D.L.21, which shared the NA-16 fuselage structure, however it proved too difficult to produce and an entirely new design (the I.Ae. D.L.22) of similar configuration, but structurally different and optimized to available materials was built instead.
Split into simpler sentences: D.L.21, which shared the NA-16 fuselage structure. However it proved too difficult to produce and an entirely new design (the I.Ae. D.L.22) of similar configuration, but structurally different and optimized to available materials was built instead.