Breezier suits with a more fluid fit are gaining ground after several seasons of slim- to snug-fitting trousers and close-cut jackets. New designs from Ermenegildo Zegna, Ferragamo, Lanvin, Fendi, and Boglioli emulate the looser-fitting styles worn in the ’40s and ’50s—think sharply pleated, straight-legged trousers with a slimming high waist and suit jackets with broad (but not bulky) shoulders. Though relaxed, these designs never slack on style. Here are a few of our favorite new loose looks.<…