Heat the oil in a large ovenproof nonstick frying pan over medium-high heat. Season chicken with salt and pepper and cook until browned on one side, about 5 minutes, then turn over and cook a few minutes more.
Transfer the pan to the oven and roast until the chicken is cooked through, about 12 minutes. Let rest for at least 5 minutes before cutting into ½-inch-thick slices.
To assemble, divide rice between four bowls and top each with some of the sliced chicken, zucchini, avocados and tomatoes. Drizzle each bowl with 2 tablespoons of dressing and serve immediately.
For safe meat preparation, reference the USDA website.