Beat yolks until thick and lemon colored. Gradually add milk, beating constantly. Add lime rind and juice; mix well.
Beat egg whites (at room temperature) until stiff peaks form. Gently fold whites into lime mixture. Spoon mixture into pastry shell. Bake at 325° for 25 minutes. Cool to room temperature. Chill at least 3 hours. (Pie will set upon cooling.)
Beat whipping cream until foamy. Gradually add sugar, beating until soft peaks form. Stir in vanilla. Garnish top of pie with whipped cream before serving.