Prepare a crumb base mixing 2 cups ground graham crackers with ½ cup unsalted butter, melted (plain or browned), until it resembles wet sand.
Line a 9x13-inch (23x33cm) pan with 2-inch sides with aluminum foil or parchment paper, letting it hang over the two long sides (the short sides won’t have foil). Pat the crumb mixture evenly over the bottom. Refrigerate while making the filling.
Beat 2 cups whipping heavy or heavy cream, cold, in a medium bowl until medium-firm peaks form when the beaters are lifted. The tip will fall slightly, and the cream will have consistency but not be completely firm.
Beat 21 ounces cream cheese until smooth in a large bowl. Add the half whipped cream to the smooth cream cheese, and beat until beginning to thicken, about 1-2 minutes. The peaks when you lift the beaters should be quite firm but with a slight drop.
Stir in 1 can sweetened condensed milk, 2 teaspoons lemon zest, and ½ teaspoon vanilla extract, and mix well.
Pour the cheesecake mixture over the crumb crust in the prepared pan.
Add dollops of 1 cup passionfruit curd all over the batter. With a smooth-bladed knife, swirl it lightly. You might not use all of the curd.
Refrigerate for 2 hours, or until it's firm enough to cut. Or freeze it, well covered in plastic wrap first, and then aluminum foil.
Serve cold. Take out of the freeze about 15 minutes before serving. Cut into squares and serve.