Whip together the cream, grated lemon and orange rinds and sugar in a large bowl until the mixture starts to thicken. Add the lemon and orange juices and whisk again until the mixture thickens.
Whip, in a separate large, perfectly clean bowl, the egg whites until soft peaks form, then fold into the citrus mixture. Spoon the mousse into 4 glasses and chill in the refrigerator. Decorate with lemon and orange rind strips.