Step 1

In a small bowl combine Italian seasoning, salt, and black pepper. Sprinkle mixture evenly over all sides of chicken; rub into chicken with your fingers. Place chicken in a 3-1/2- or 4-quart slow cooker.

Step 2

Add onion, mushrooms, and garlic. In a bowl combine tomatoes and vinegar; pour over chicken mixture in cooker.

Step 3

Cover and cook on low-heat setting for 4 to 5 hours or on high-heat setting for 2 to 2-1/2 hours. If using low-heat setting, turn to high-heat setting. Stir in zucchini and sweet pepper. Cover and cook on high-heat setting for 30 minutes more.

Step 4

Meanwhile, in a small bowl combine mayonnaise and pesto. Spread pesto mixture evenly over cut sides of bread.

Step 5

Transfer chicken to a cutting board. Using a slotted spoon, spoon vegetable mixture onto bread bottom. Discard cooking juices. Thinly slice chicken. Arrange chicken slices over vegetables. Add basil and bread top. Cut loaf into 6 or 8 serving-size portions.