Prepare Sunny Lemon Pound Cake as directed on package with butter and water. Set aside icing mix package. Cool cake completely; cut cooled pound cake into roughly 1-inch cubes.
In a medium-size mixing bowl, fold instant lemon pudding powder into whipped topping until well blended.
Using a stand or hand-held electric mixer, whip heavy cream until soft peaks form. Add contents of icing mix package and whip an additional 1-2 minutes.
In a trifle bowl or large serving bowl, layer half of the pound cake cubes in the bottom of the bowl, half of the lemon cream mixture, about a cup of blueberries and whipped cream. Repeat cake, lemon cream, blueberries and whipped cream layers.
Garnish top whipped cream layer with additional blueberries. Sprinkle blueberries with lemon zest and arrange lemon slices around sides of bowl, if desired.