South must run 4 diamonds and one spade. East can delay by pitching spades on diamonds, but on the spade, they must discard.

What does East keep? If they pitch a club, declarer plays, club Ace, spade to hand, 4 rounds of clubs (now good). At trick twelve the heart queen is lead, and East having only hearts left, must concede a 12th trick.

So what if East pitches a heart? Another spade is cashed. Now if East pitches another heart (now down to AJ), the Queen of hearts is lead. If East wins, dummy is good. If they duck, a club to dummy, the Queen of spades for a diamond pitch, and a low heart for the losing club, also uses East as a stepping stone to South’s good clubs.

If East pitches Heart, but then a club, down to 0=3=0=4: Club to dummy, queen of spades pitching the losing diamond, low heart. If East ducks south takes the rest (all 13), so they win, but now are endplayed in hearts to dummy, or just a stepping stone to South’s good clubs.

At double dummy, 6S by North is a little bit easier than this.

6S on a diamond lead: lead the Q of hearts. if ducked or if won and no trump shift, score 1 heart, 2 clubs, and 2 diamonds and cross ruff for 7 spades (when in hand with QT.K.-.- exit with the heart to score the last two).

If won, and a trump shift. ruff a diamond, Ace of clubs, trump to dummy…

6S on a trump lead: Ace and ruff a diamond, Ace of clubs, (all critical) then a heart.

If won and a club, win and cash the trump. If a trump shift, win…

… dummy has 3 good diamonds and KQJx of clubs. Cash 3 diamonds and then run clubs. West must follow until trick 11, and then is caught, as North has QT of spades, and the good K of hearts.