MICROWAVE chocolate and 1/2 cup COOL WHIP in microwaveable bowl on HIGH 1 to 1-1/2 min. or until chocolate is completely melted and mixture is well blended, stirring after 1 min. Stir in zest. Spread onto bottom of crust; sprinkle with half the nuts.
BEAT pudding mixes and milk in medium bowl with whisk 2 min. Stir in 1-1/2 cups of the remaining COOL WHIP; pour into crust.
COVER with remaining COOL WHIP. Refrigerate 3 hours or until firm. Sprinkle with remaining nuts.