Cook onions with red bell peppers in a microwave, for 3 minutes, to soften. Place chicken breasts in bottom of crock-pot and add garlic, Italian seasoning, and a little salt and pepper. Add cooked onions and red bell peppers, zucchini, beans, fire-roasted tomatoes, and tomato sauce. Mix well. Set on low heat for 5 hours or on High heat for 2½ hours.
When ready, remove chicken breasts from crock-pot, cool slightly, and shred with hands or use two forks. Place back in stew and mix together well.
Serve it just as is, in a bowl. Top with Parmesan cheese, if desired. Or, serve over zoodles, steamed cabbage, veggies, brown rice, baked potato, mashed potato, or toasted bread, if desired.