In a large mixing bowl, whisk together milk and sour cream. Whisk in two boxes of  lime JELL-O and to combine.

Fold in half your tub of whipped topping, reserving the half for trifle assembly.

Place lime mixture into the fridge to set for a few minutes.

Cut off all the dark edges off your frozen pound cake with a serrated knife.

Cut your pound cake into 1 inch cubes. (It is easier to cut the pound cake when it is still frozen.)

Slice two of your fresh limes for garnish.

To assemble, place 1/3 of the pound cake into the bottom of your trifle bowl.

Push the pieces out to the sides.

Add half of your lime mixture.

Add another 1/3 of your pound cake pieces.

Top that with 4 oz of Cool Whip. (This is half of what is remaining.)

Add the remaining pound cake pieces.

Add the remaining half of your lime mixture.

Fill a piping bag (or a ziploc bag with one end cut off) with the remaining 4 oz of Cool Whip and decorate the outside edge of the top of your trifle.

Garnish with sliced fresh limes and the zest of the third lime.

Refrigerate until ready to serve.