Quick Chicken with zucchini

4 boneless skinless chicken breasts 1 red onion , large sliced thinly 2 zucchini , sliced about 1/2 inch thick 28 ounces diced tomatoes 8 ounces button[...]

2 tablespoons olive oil 1 pound skinless, boneless chicken breast halves - cut into bite-size pieces 2 cloves garlic, minced 1 medium onion, cut into 1/2-inch[...]