Chill a large mixing bowl and beaters in the freezer for 15 minutes. Pour the cold heavy cream into the chilled bowl.
Beat the cream on medium speed until it begins to thicken, about 1 minute. Add the powdered sugar and continue beating until soft peaks form.
Add the vanilla extract and beat on medium-high speed until stiff peaks form, about 1-2 minutes more. Be careful not to overbeat or the cream will become grainy.
In a large trifle bowl or 6-8 individual glasses, start layering. Place a layer of pound cake cubes at the bottom, using about one-third of the cake.
Spoon half of the lemon curd over the cake layer, spreading gently to the edges. Top with one-third of the whipped cream, smoothing with a spatula.
Repeat the layers: another third of the cake, the remaining lemon curd, and another third of the whipped cream.
Finish with a final layer of pound cake cubes and top with the remaining whipped cream. Smooth the top and garnish with fresh lemon zest if desired.
Cover tightly with plastic wrap and refrigerate for at least 2 hours or up to 24 hours before serving to allow the flavors to meld and the cake to soften slightly.
