01 - Place the chicken breasts in an even layer across the bottom of the slow cooker.
02 - Evenly sprinkle the ranch seasoning mix, garlic powder, onion powder, smoked paprika, and black pepper over the chicken breasts.
03 - Pour the chicken broth and the entire can of diced tomatoes with green chilies, including the juices, over the seasoned chicken.
04 - Cover the slow cooker and cook on low for 4 to 5 hours, or on high for 2 to 3 hours, until the chicken is fork-tender and cooked through to an internal temperature of 165°F.
05 - Transfer the chicken to a cutting board and shred using two forks. Return the shredded chicken to the slow cooker, stir to combine with the cooking juices, and let it rest for 10 minutes to absorb the flavors.
06 - Warm the taco shells or tortillas in a dry skillet over medium heat for about 30 seconds per side, or according to package directions.
07 - Divide the ranch chicken evenly among the warmed taco shells or tortillas. Top with shredded lettuce, cheddar cheese, sour cream, diced tomatoes, and fresh cilantro as desired. Serve immediately.