Add boiling water to gelatin mixes in large bowl; stir 2 min. until completely dissolved.
Place 1 cake cube in each muffin cup; pour gelatin over cake to fill cup completely. Refrigerate 2 hours or until set.
Beat cream cheese in medium bowl with mixer until creamy. Gradually add sugar, beating until blended after each addition. Gently stir in COOL WHIP and lemon zest until blended.
Fill pastry bag fitted with star tip with cream cheese mixture. Pipe decorative dollop of cream cheese mixture on top of each trifle.