In a slow cooker, mix together the salsa, lime juice and zest, taco seasoning, and optional black beans and jalapeño pepper.
Add the chicken and flip to coat with the salsa mixture.
Cook on low heat for approximately 6 hours (or 3 hours on high) or until the chicken is cooked through. At this point, you may remove the chicken to a plate and shred with two forks before returning to the slow cooker. Or you may serve the chicken breasts whole.
Stir in the 1/4 cup cilantro and serve over rice or your grain of choice. Sprinkle with cheese, and garnish with additional cilantro, if desired.