Combine the blueberries, pineapple, oranges, melon, lemon juice, lemon zest, sugar, and pineapple juice in a large skillet. If desired, stir in the yogurt to make the mixture more creamy. Cook and stir over medium-high heat until the sugar dissolves and the fruit softens, 3 to 5 minutes.
Place fruit mixture into a blender or the bowl of a food processor; blend or pulse until smooth. Spoon into a freezer dish. Chill until mixture becomes slushy, about 20 to 25 minutes, or until desired consistency. Serve garnished with fresh mint leaves.
