Combine the carrot, parsley, onion, garlic, lemon zest, salt, and ground pepper in a small blender or food processor. Process until finely chopped and transfer to slow cooker. Add chicken and butter and mix. Cook on Low for 5 to 6 hours.
Stir in Neufchatel cheese, chicken soup, and peas. Cook on High until heated through, about 30 minutes.