Combine cheesecake filling, lemon curd, and lemon zest in a bowl; stir well. Add mixture to a piping bag or large zip-top bag. Make a small cut in the corner of the bag.

Use a paring knife to make a small cut into the side of each croissant. Create an opening large enough to pipe the filling into. Fill each roll with about 3 tablespoons of filling. Place filled croissants on a wire rack set inside a lined baking sheet to catch excess drippings.

Add sugar and water to a small saucepan and bring to a simmer over medium-high heat. Reduce to medium low and cook, without stirring, until lightly golden brown, about 10 minutes.