Translating red-carpet glamour and architectural tailoring — Zac Posen’s most dominant signatures — to the far more casual contemporary market can make for challenging work. As his Zac Zac Posen evolves, he is getting more adept at navigating the transition between designer and contemporary. He considered “how to bring a dressed-up element into street style,” he said, retaining all the polish of his main collection while infusing the spring lineup with an air of relaxation. Long dresses, including one in a sunset print adapted from one of Posen’s Instagram snaps, were cut with breathing room and handkerchief hems. The latter took a more structured turn on crisp poplin shirts with asymmetric hems. Knits were also strong, in a popcorn texture that came on cropped tops and short dresses.