The Shroud and the Mona Lisa contain many common points such as to generate suspicion that they are actually two separate parts of a single work.
The Shroud and the Mona Lisa not only contain graphic parts that seem designed specifically to be overlapped with each other, but they also contain references to correctly display and overlay.
Personally I do not believe that the creation of the Shroud is the result of a specific commission proposed by the Savoy but I think the Shroud of Leonardo was ready because it was the result of previous experiments tending to prove the falsity and the easy reproducibility of such a relic.
In the realization of his Shroud Leonardo, however, takes a number of precautions so that the truth will emerge in the future, in order to prepare or modify the Mona Lisa so that superimposing the two images it is quite unobjectionable that the achievement is yours.
And it was photographic. Yes, apparently so if you believe Littleflower. Forget the shroud, the implications for the Mona Lisa are devastating.