Complex sentence: On that day, with two partners, Mallet founded Société Mallet, Mélandri et de Pitray, the predecessor of the Zodiac firm; the new venture specialized in the design and construction of airships.
Split into simpler sentences: On that day, with two partners, Mallet founded Société Mallet, Mélandri et de Pitray, the predecessor of the Zodiac firm. The new venture specialized in the design and construction of airships.