In a medium mixing bowl fold together the yogurt, whipped topping, and shredded lime peel.
To assemble individual trifles, coarsely crumble one cookie into each of the 6 cups. Spoon about 3 heaping tablespoons of the yogurt mixture in each cup on top of the crumbled cookie. Spoon about 1/3 cup of the chopped mangoes into each cup. Crumble another cookie into each cup, and top with remaining yogurt mixture (about 3 tablespoons in each cup).
Cover and chill for at least 1 hour or up to 24 hours. Before serving, garnish with mango slices and lime peel, if desired. Makes 6 servings.