Prepare the sauce: In a small bowl, whisk together the soy sauce, rice vinegar, sesame oil, and sweetener if using. Set aside.
Heat the avocado oil in a large skillet or wok over medium-high heat.
Add the chicken pieces and cook for 5 to 7 minutes, stirring occasionally, until browned and cooked through. Remove the chicken from the skillet and set aside.
Add the minced garlic and grated ginger to the same skillet. Cook for 30 seconds until fragrant.
Add the sliced zucchini and bell pepper to the skillet. Stir fry for 4 to 5 minutes until the vegetables are tender-crisp.
Return the cooked chicken to the skillet.
Pour the prepared sauce over the chicken and vegetables. Stir constantly for 1 minute.
If you want a thicker sauce, whisk the xanthan gum into 1 tablespoon of cold water, then stir this slurry into the skillet. Cook for 30 seconds until the sauce thickens slightly.
Remove from heat. Garnish with sesame seeds before serving.
Notes
For a lower-carb vegetable addition, substitute mushrooms for the bell pepper.
If you do not need this recipe to be keto, you can substitute regular sugar for the sweetener and use regular soy sauce.
To ensure tender chicken, do not overcrowd the pan when searing. Cook in batches if necessary.