In 1-quart saucepan, combine gelatin and 1/3 cup sugar.
In small bowl with whisk, beat egg yolks, water, lemon peel and lemon juice. Stir into gelatin mixture.
Cook over medium-low heat; stirring constantly, until mixture thickens and coats spoon. Remove saucepan from heat.
In large bowl, with mixer at high speed, beat egg whites until soft peaks form; gradually sprinkle in 1/2 cup sugar, beating until sugar is completely dissolved.
Use whisk to gently fold lemon mixture into egg whites just until blended.
Pour into piecrust; use rubber spatula to even out surface. Refrigerate pie until lemon chiffon filling is set.
To serve, spoon whipped cream in mounds around pie edge and sprinkle with shredded lemon peel.