For the chocolate strudel, separate the eggs. Beat the yolks with the powdered sugar, lemon zest and rum until foamy.
Beat egg whites with granulated sugar until creamy and mix with yolk mixture. Carefully fold in the almonds and spread half of the mixture onto a strudel sheet coated with melted butter.
Sprinkle chocolate on top and roll up. Place the strudel on a baking sheet lined with baking paper and do the same with the second strudel sheet.
Bake at 200° for approx. 25 minutes. Sprinkle the chocolate strudel with cocoa after cooling.