01 - Place chicken breasts in the bottom of the slow cooker in a single layer.
02 - Sprinkle ranch seasoning mix, garlic powder, onion powder, smoked paprika, and black pepper evenly over the chicken.
03 - Pour chicken broth and the entire can of diced tomatoes with green chilies, including juices, over the seasoned chicken.
04 - Cover and cook on low for 4 to 5 hours, or on high for 2 to 3 hours, until the chicken is tender and reaches an internal temperature of 165°F.
05 - Remove the chicken from the slow cooker and shred using two forks. Return the shredded chicken to the pot, stir to combine with the cooking juices, and let it rest for 10 minutes to absorb the flavors.
06 - Warm taco shells or tortillas in a dry skillet, oven, or microwave until pliable.
07 - Divide the ranch chicken evenly among the warmed taco shells, then top with shredded lettuce, cheddar cheese, sour cream, diced tomatoes, and fresh cilantro as desired. Serve immediately.