Wash and dry the greens. Slice them in narrow ribbons and set aside. Peel the jicama and sliver it into very thin matchsticks. Cut the green beans in half at a severe angle. Whisk the lime zest, juice, and olive oil together with a few pinches of salt. Slice the scallions into long, thin slivers.
Toss the greens with the jicama, green beans, scallions, mint, and a few pinches of salt. Then dress the salad with enough of the vinaigrette to coat lightly but thoroughly. Season with pepper.