In a large bowl, mash bananas; they should measure about 3⁄4 cup. Add eggs and oil; whisk to mix. Stir in mix.
Divide batter evenly into pans. Smooth tops as best you can.
In two batches, microwave on high 3 min. Rest in pan 5 min; invert onto Cooling Racks and gently squeeze and push to release. Or, place Mini Bundt Cake Pans on two 1⁄4 Sheet Pans. Bake in preheated 350° F for 20 min or until a toothpick inserted in the centre comes out clean. Cool in pan 10 min. Invert on Cooling Racks and gently squeeze and push to release. Allow to cool completely before glazing. Refrigerate, if desired, to cool quickly.
In a bowl, whisk together sugar, milk, and lemon juice until smooth. Spoon over cooled cakes and top with zest, if desired. Glaze will set and harden as it sits.