Lightly coat the bottom of a 5- to 6-quart slow cooker with nonstick cooking spray. Place chicken breasts in a single layer in the slow cooker and sprinkle with garlic powder and lemon zest. Pour chicken broth and Caesar dressing over the chicken.

Cover and cook on Low for 5 hours or on High for 2 1/2 hours or until an instant-read thermometer registers 165°F (74°C).

Remove chicken from the slow cooker and allow to cool slightly on a cutting board before shredding or chopping into bite-sized pieces.

Stir the pasta into the dressing mixture in the slow cooker. Cover and cook on High for 20 to 30 minutes or until pasta is tender.

Stir in cream cheese and 1/4 cup of Parmesan cheese until melted. Add shredded chicken, and parsley; stir to combine. Turn cooker off and let pasta mixture stand, uncovered, to allow sauce to thicken slightly for 10 minutes.