Preheat your oven to 350 degrees.
Grease a 9x13 baking dish.
In a large bowl whisk together the cake, mix, eggs, water and oil the box calls for.
Pour the batter into the prepared pan.
Bake 25-30 minutes or until toothpick inserted in center comes out clean.
Cool slightly.
Using a large straw or end of a wooden spoon poke holes all over the cake.
In large mixing bowl whisk together the sweetened condensed milk, lime juice, whipping cream, lime zest and a few drops of green food coloring.
Pour the filling all over cake using a spoon to get the filling into all the holes.
Spread the whipped cream evenly over the top of the cake.
Garnish with more lime zest.
Refrigerate at least 1 hour.
Slice and serve!