Use a 6-quart slow cooker. Put the chicken into the bottom of your cooker. Add the onion and whole garlic cloves. Toss the cauliflower and zucchini on top and pour in the tomatoes. Add all of the spices and stir in chicken broth, taking care to not crumble the cauliflower. Cover and cook on low for 6-8 hours, or on high for about 5 hours.