For the watermelon layers, cut 2 slices, each 1-inch thick, from both the watermelon and yellow watermelon. Stack the 2 slices of each kind of watermelon on top of one other and press an 8-inch bowl down on top. Use a knife to trace the bowl and cut the pieces of watermelon into circular slices. Remove the rind and transfer the circular pieces of watermelon to a clean kitchen towel. Cover them with a second towel and let the excess liquid drain out for at least 6 hours, preferably overnight.
For the coconut cheesecake cream, whip the heavy cream in a medium-sized mixing bowl. Stir together the cream cheese, coconut milk, powdered sugar, salt, and lemon & lime zest, then carefully fold in the whipped cream. Transfer the coconut cheesecake cream to the refrigerator and chill for 1 hour.
Once the watermelon has drained, place 1 slice of yellow watermelon on a large plate and spread an even layer, about 1/2 inch thick, of coconut cheesecake cream on top.
Place 1 slice of watermelon on top of the first layer of coconut cheesecake cream. Continue adding layers to the watermelon popsicle, alternating between coconut cheesecake cream and watermelon slices, making sure the final layer is a slice of watermelon. Transfer the layered watermelon to the refrigerator and chill for 1 hour.
Once the layered watermelon has chilled, remove it from the fridge and insert 12 evenly spaced wooden skewers into it, making sure the wooden skewers pierce the final layer of watermelon. Line up the wooden skewers in a row and cut the layered watermelon into even slices.
Use a double boiler to melt the milk and white chocolate in tall shot glasses. Dip the layered watermelon skewers into the melted chocolate.
Cover the watermelon popsicles coated in milk chocolate with nut topping, and the popsicles coated in white chocolate with toasted coconut flakes. Let the melted chocolate and toppings set for 5 minutes.