Place the chicken in the base of a crock pot. In a mixing bowl, whisk together the balsamic vinegar, syrup, garlic, salt, and chili flakes.
Pour over the chicken.
Cover with the lid and cook on high for 3 hours.
Add the onion, sliced peppers, and sliced zucchini to the crock pot. Cook for one more hour.
Mix the arrowroot powder and water together to form a smooth mixture.
Pour into the crockpot and mix into the cooking liquid by tossing around the chicken and vegetables. Let cook for another 10 minutes, or until liquid thickens enough to coat the chicken and vegetables. Add cilantro to the chicken and toss to distribute.