Cut the pound cake into 8 pieces, then each piece into 3 slices.
In the bottom of the ice cream container, mash about 5 to 6 strawberries, raspberries and blackberries with a fork until combined. Add the nip of liquor, replace the top and give it a good shake.
In 4 martini glasses, divide the cake pieces equally. Pour the sauce over each of the martini glasses and top with some of each kind of berry. Top with a squirt of the whipped cream and the lime zest.