Preheat Skillet on medium-high heat. Sprinkle water droplets into Skillet; when droplets bead and dance across the surface, add the chicken breasts, sear for 5 minutes and then flip over. Cover with lid and turn valve to the Steam-Seal™ position. Cook for 6-8 minutes. Once chicken is cooked, shred it and set aside.
Preheat Casserole on medium-high heat. Sprinkle water droplets into Casserole; when droplets bead and dance across the surface, add onion, carrots, celery and garlic; sauté until onions are clear. Add broth, chili powder and rice. Cover with lid and turn valve to the Steam Whistle position. When the whistle sounds, turn valve to Steam-Seal™ position, reduce heat to medium-low and cook for 8 minutes. Add squash, zucchini and shredded chicken. Cover and turn valve to the Steam Release position, continue to cook until rice is tender, about 5 minutes. Add tomatoes and serve.