Cut zucchini in half lengthwise and then into 3/4-inch slices. In a 31/2- or 4-quart crockery cooker combine zucchini, green pepper, onion, and celery. Top with chicken strips. In a small bowl combine taco sauce, bouillon granules, and cumin. Pour over chicken.
Cover and cook on low-heat setting for 6 to 7 hours or on high setting for 3 to 3 1/2 hours. Stir in rice. Cover and let stand for 5 minutes.
Warm tortillas according to package directions. Divide chicken mixture evenly among warmed tortillas. Top with shredded cheese, tomato, and green onion. Fold bottom edge of each tortilla up and over filling. Fold opposite sides in, just until they meet. Roll up from bottom. Secure with wooden toothpicks, if necessary.