Combine the chili powder, ground cumin, garlic and onion powders, and paprika in a small bowl. Trim the chicken breasts, rinse and pat them dry with paper towels. Sprinkle the spice mixture evenly over both sides of the chicken breasts. Wrap in plastic wrap and place in the refrigerator until 15 minutes before you are ready to grill.
Preheat the grill on high, covered, for about 15 minutes. Open lid and clean grate with grill brush. Turn the grill temperature down to medium-low. Wad up a couple pieces of paper towel and grab the wad with a pair of tongs. Dip the wadded paper towel into some vegetable oil, then using the tongs, brush the grates with the oiled paper towel.
Place the chicken onto the grill and cover with a disposable aluminum pan, or close the lid. Allow to cook for 6-8 minutes, long enough to create nice grill marks. Turn the breasts over and cover with aluminum pan for 6-8 minutes more. Turn grill temperature down to low and keep lid closed, cooking chicken several minutes more until internal temperature reaches 165 and juices run clear. Place chicken on cutting board and let it rest for five minutes before slicing.
In a 4-quart Dutch oven combine the chicken broth, corn, undrained tomatoes, rice, beans and green chile peppers. Bring to a boil, then reduce heat, cover, and simmer for 12 minutes. Stir in zucchini, replace cover and cook for 5 minutes more, until zucchini is tender crisp. Remove from heat, stir in cilantro.