Combine rice and veggie broth in a medium pot and cook according to directions on rice package.
Meanwhile, combine diced zucchini, red onion, red bell pepper, corn and mushrooms in a large bowl. *Note: You can also leave the corn on the cob and grill the entire cob, and cut the kernels off afterward. Just brush the corn with a little olive oil and season with salt and pepper, and grill for ~10 minutes, rotating 3 times.
Drizzle with olive oil and season with salt and pepper, and toss to combine.
Place veggies in a large grill pan (or wrap in foil if you don't have a grill pan).
Cook over medium heat on your grill for 10-15 minutes, stirring often.
Let cool.
While veggies are cooling, make your chipotle sauce.
Add Greek yogurt, mayo, chipotles en adobo sauce, lime juice, cumin, chili powder, garlic powder, and salt to food processor and pulse until pureed.