1. Prepare the Chicken: Start by cutting your boneless, skinless chicken breasts or thighs into uniform 1-inch pieces. This ensures they cook evenly and become wonderfully tender in the stew.

2. Combine Ingredients in Slow Cooker: Place the cut chicken into the bottom of your slow cooker. Add the chopped onion, minced garlic, dried oregano, dried basil, black pepper, and salt over the chicken. Pour in the chicken broth and the undrained can of diced tomatoes.

3. Stir Gently: Give all the ingredients a gentle stir to combine them well. Make sure the chicken is mostly submerged in the liquid and spices are distributed evenly.

4. Set and Cook: Cover your slow cooker with its lid. Cook on the LOW setting for 6-8 hours, or on the HIGH setting for 3-4 hours. The chicken should be cooked through and easily shredded with a fork when done.

5. Add Zucchini: About 30-45 minutes before the end of the cooking time (or when the chicken is almost done), stir in the zucchini half-moons. This timing prevents the zucchini from becoming overly mushy and helps it retain a pleasant texture.

6. Finish Cooking: Replace the lid and continue cooking until the zucchini is tender-crisp and the stew is heated through. The stew should be bubbling gently and fragrant.

7. Taste and Adjust: Carefully taste the stew and adjust the seasoning with additional salt and pepper if needed.

8. Serve Warm: Ladle the warm stew into bowls. If desired, garnish with fresh chopped parsley before serving for a burst of color and fresh flavor.