For the first lemon layer, add frozen lemon flavored ice cream to a mixer. Add lemon zest and mix until smooth, but not melted. Spread evenly over the cooled pretzel crust. Top lemon ice cream layer with fresh raspberries. For the vanilla bean layer, add the vanilla bean ice cream to mixer. Add 1/2 cup of fresh raspberries and mix until smooth. Spread mixture over the fresh raspberries. Cover and freeze for 2 hours. Remove from freezer, top with remaining 1/2 cup of fresh raspberries, chocolate shavings, and a dollop of whipped cream. Serve immediately.