Launched in 2004 as Ermenegildo Zegna's younger, more fashion-forward collection, the Z Zegna line now accounts for about 15 percent of its parent company's bottom line. Design head Alessandro Sartori grew up in a small mountain town renowned for the wool it produced for Zegna, and Sartori—his surname is Italian for "tailor"—has spent virtually his entire career with the company.