In a medium saucepan, whisk together granulated sugar, lemon zest, and eggs over medium heat until the mixture turns light and frothy, about 2-3 minutes. Gradually add fresh lemon juice, stirring constantly. Cook for an additional 5 minutes until thickened. Remove from heat and whisk in cold butter and vanilla until smooth. Strain the mixture and let cool in the refrigerator for at least 2 hours.

In a large mixing bowl, combine softened low-fat cream cheese, plain Greek yogurt, granulated sugar, and vanilla extract. Beat on medium-high speed until velvety smooth, about 2-3 minutes. Set aside.

Layer the parfaits by adding crushed graham crackers as the base, then a layer of cheesecake mixture, followed by lemon curd. Repeat until ingredients are used up.

For optional whipped cream topping, whip heavy cream until soft peaks form, then spoon or pipe onto each parfait.

Chill parfaits in the refrigerator for at least 30 minutes before serving, and enjoy with a sprinkle of lemon zest or mint leaves.