With Messerschmitt concentrating on the design and construction of combat aircraft, The
Luftschiffbau Zeppelin company was commissioned with designing an enlarged variant of the
Messerschmitt Me 323 "Gigant" in early 1943. Initially, Luftschiffbau Zeppelin only attempted to improve on the Me 323‘s design, resulting in the ZMe 323 G and ZMe 323 H variants, which failed to meet the Luftwaffe’s expectations and were never constructed. Following this setback, Luftschiffbau Zeppelin chose to significantly redesign the aircraft into what would become known as the ZSO 523. Due to a lack of available specialists at Luftschiffbau Zeppelin, the project was subcontracted to French aircraft manufacturer
SNCASO. The ZSO 523 was planned to be a high-wing monoplane like the Me 323 but of larger proportions. Unlike the Me 323, it was to have both a front and rear loading ramp, and a
twin tail. The aircraft was noteworthy for having one of the most spacious cockpits of any World War 2 era German aircraft, located above of the fuselage. The crew consisted of 5 people; a captain, a co-pilot, a radio operator and navigator, only one flight mechanic, unlike its predecessor, and (optionally) a loading attendant. The ZSO 523 was to be powered by six
Gnome-Rhône 18R engines providing 2200 hp (later 2500 hp) of thrust each. The landing gear was to consist of 8 hydraulically retractable wheels, and was also designed to lower the aircraft's fuselage to ground level for loading and reloading. ==Mockup==