In a medium pot, bring 2 quarts of water to a boil. Add the potatoes and cook until fork-tender, about 8-12 minutes. While the potatoes are cooking, remove the husk and silks from the corn and steam the corn for 12 minutes. Drain the potatoes, cut the corn from the cob, and place both in a large bowl. To the bowl add the peaches, zucchini, tomato, pepper and green onion.
FOR THE DRESSING & TO FINISH:
In a small bowl add the orange zest and juice. Whisk in the olive oil, garlic, Dijon mustard, salt and pepper. Pour the dressing over the potato mixture. Toss and chill for at least 1 hour before serving.