STIR boiling water into dry gelatin mix in large bowl at least 2 min. until gelatin is completely dissolved. Stir in lemon zest and juice.
ADD ice cream; stir until ice cream is completely melted and mixture is well blended. Refrigerate 15 to 20 min. or until mixture is very thick and will mound. Spoon into crust.
REFRIGERATE 2 hours or until firm. Store leftover pie in refrigerator.