Preheat the oven to the temperature specified on the cake-mix box. Line two 12-cup muffin tins, or plan to bake in batches.
Mix the dry cake mix, sour cream, eggs, and lime zest until smooth; do not add the additional ingredients listed on the box. Fill the cups two-thirds full.
Bake for the box's cupcake time and cool slightly. Poke holes in each cupcake with a fork.
Whisk the condensed milk, evaporated milk, heavy cream, and optional tequila. Spoon it gradually over the cupcakes so it can soak in.
Refrigerate for at least 2 hours. Top with whipped cream and lime zest before serving.