I guess the heading is slightly inaccurate, as the chance of making this grand after the lead is 1 in 10,400,600. You have a bidding misunderstanding, but the play's the thing as they say. How do you play, single-dummy, on the diamond lead. Keen students of the feature "an unusual squeeze" will find this duck soup.
Corrected (I hope) after cyberyetis’comments.
A similar deal, something like this,
constructed for an article on 3-trick squeezes,
(published in Bridge-Magazine, about half a century ago).
6N by South on a ♠ lead.