Complex sentence: He joined the auto manufacturing conglomerate FIAT S.p.A., headquartered in Torino, Italy, and in 1973 was moved to Ferrari, where he became Enzo Ferrari's assistant and, in 1974, manager of the Scuderia.
Split into simpler sentences: He joined the auto manufacturing giant and conglomerate FIAT S.p.A. which is headquartered in Torino, Italy. However in 1973 FIAT moved him to Ferrari, where he promptly became Enzo Ferrari's assistant and, in 1974, manager of the Scuderia.