Dry the turkey breast thoroughly with paper towels and gently lift the skin to apply seasoning beneath if it has skin.
Combine melted butter, olive oil, minced garlic, salt, pepper, garlic powder, onion powder, paprika, thyme, rosemary, sage, and lemon zest in a bowl.
Coat the entire turkey breast evenly with the butter mixture, making sure to get some under the skin.
Arrange the sliced onion, chopped celery, carrot, and any leftover garlic at the base of your crockpot.
Pour in the chicken or turkey broth along with Worcestershire sauce over the vegetables.
Set the turkey breast on top of the vegetables, cover the crockpot, and cook on LOW heat for 5 to 6 hours, adjusting time based on size (about 5 hours for 4 lbs and up to 6 hours for 6 lbs), until the internal temperature reaches 165°F.
For a crispier exterior, broil the cooked turkey in the oven for 4 to 5 minutes if desired.
Allow the turkey to rest for 10 to 15 minutes before slicing and serving.