Prepare Lemon Simple Syrup: Combine ¼ cup sugar and ¼ cup water in a small saucepan. Bring to a gentle simmer; cook, stirring occasionally, until the sugar dissolves, about 2 minutes. Stir in lemon zest; remove from heat. Cover and let steep for 5 minutes. Refrigerate, stirring occasionally, until cool, about 20 minutes. Strain through a fine-mesh sieve; discard the zest.
Prepare Whipped Lemonade: Combine the cooled syrup, 1 cup coconut milk, ½ cup lemon juice, 2 cups ice and ¾ cup raspberries in a blender. Blend until the ice is crushed and the mixture is slushy, about 30 seconds. Divide among 4 glasses and serve immediately.