1. Prepare your oven for roasting. Preheat to approximately 375ºF, varying by oven. In a large bowl, toss the corn and zucchini with 1 tablespoon of the olive oil and season with salt and pepper. Alternately, you can grill the vegetables over moderate heat. Roast or grill until slightly charred and crisp-tender, about 10 minutes for the zucchini and 15 minutes for the corn, again, varying by oven. Transfer to a cutting board and let cool. Cut the kernels off the corn and cut the zucchini into half-moons. Transfer to a large bowl.
2. Meanwhile, in a large saucepan of salted boiling water, cook the orzo until al dente. Drain and rinse under cold water to cool. Drain well and spread the orzo out on a baking sheet; pat dry with paper towels.
3. In a large bowl, whisk the mayonnaise with the remaining 3 tablespoons of olive oil and the lime juice, shallot, chile powder and ½ cup of the cilantro; season with salt and pepper. Add the orzo, corn, zucchini and the remaining chopped cilantro and mix well. Transfer to a platter. Using a vegetable peeler, shave the cheese all over the top, garnish with green onions, and serve.