Very recently, the first mathematical runtime analyses for the NSGA-II, the most common multi-objective evolutionary algorithm, have been conducted (Zheng, Liu, Doerr (AAAI 2022)). Continuing this research direction, we prove that the NSGA-II optimizes the One-JumpZeroJump benchmark asymptotically faster when crossover is employed. This is the first time such an advantage of crossover is proven for the NSGA-II. Our arguments can be transferred to singleobjective optimization. They then prove that crossover can speedup the (µ + 1) genetic algorithm in a different way and more pronounced than known before. Our experiments confirm the added value of crossover and show that the observed speed-ups are even larger than what our proofs can guarantee.