Empty both packages of peach gelatin into a bowl. Stir in 2 cups of the boiling water until the gelatin is fully dissolved. Stir in 3/4 cups of the cold water and the peach schnapps or water. Refrigerate mixture until thickened. If using canned peaches, drain well. Arrange some of the peach slices in a formation in the bottom of a 9-cup mold. Reserve remaining peaches. Spoon thickened peach gelatin into the mold over te arranged peach slices. Refrigerate until gelatin is set but not firm.
Meanwhile, in a separate bowl, sprinkle unflavored gelatin over 1/2 cup of the cold water and allow the gelatin to absorb the water. Stir in 1 1/2 cups of the boiling water until gelatin is fully dissolved. Stir in sweetened condensed milk until the mixture is smooth. Refrigerate mixture until slightly thickened. Chop up any remaining peach slices and fold into sweetened condensed milk mixture. Gently spoon into the mold over the peach gelatin layer. Refrigerate until firm. Unmold and serve.