Cube the Velveeta cheese. Put the cheese and milk in a heavy bottomed pot and heat on low until melted, stirring frequently. When the cheese is melted, stir in taco seasoning, tomatoes and chilies, black beans, and corn. Heat until dip is warm through again. Fold in the chicken, lime zest, and lime juice until well combined. If the dip is too thick, thin with a little more milk.