Preheat the oven to 375 degrees F. Lightly coat a 6-cup muffin pan with cooking spray. Prepare the corn muffin batter as the label directs, then stir in the flour, lemon zest and vanilla. Divide the batter evenly among the muffin cups. Bake until the edges are set and the centers are soft but not wet, 10 to 12 minutes. Meanwhile, toss the strawberries and strawberry preserves in a bowl and set aside. Remove the corn cakes from the oven. Gently press the back of a teaspoon into the center of each to make an indentation about one-third of the way into the cake. Spoon about 2 teaspoons of the strawberry mixture into each indentation, pressing to tightly fill. (Reserve the remaining berry mixture for topping.) Return the cakes to the oven and continue baking until just golden, about 5 more minutes. Let the cakes cool in the pan on a rack, 5 minutes, then remove from the pan and let cool 10 more minutes. Meanwhile, beat the cream and confectioners' sugar with a mixer until soft peaks form. Top the cakes with the remaining berry mixture and serve with the whipped cream.