Make cupcakes. Preheat oven to 350° F. Line standard muffin pan with baking cups.
In large bowl, combine cake mix, Margarita mix, egg whites and vegetable oil using electric mixer. Stir in lime zest; mix completely. Fill prepared pans 2/3 full.
Bake 22-24 minutes or until toothpick inserted in center of cupcake comes out clean.
Cool in pan on cooling rack 5-8 minutes. Remove cupcakes from pan; cool completely.