Novak Djokovic is through to the French Open semifinals after outclassing Alexander Zverev in a 4-6, 6-3, 6-2, 6-4 win Wednesday night. Djokovic, 38, is a decade older than Zverev, but he made his opponent look like he was stuck in the past with a performance full of variety and inventive angles that contrasted sharply with the German’s one-dimensional baseline play.