Very hard puzzle! Took me a very long time.    


Win DA, Cash DK. Cross to dummy with a trump. 
Cash 3 clubs (pitching 3  hearts) and ruff a club. 
If West over-ruffs you are cold, 
you can ruff last  club and enter dummy with either the trump or heart Ace
and squeeze East  out of best heart or 87D. 
If pitch diamond, then you can pitch QD and cash  J and 4 of Diamonds.
So West pitches heart. 
Now trump to dummy and ruff last club. 


If West  overruffs this time, the same squeeze against East is reached. 
So West  pitches another heart.    
Now South cashes QD. If west ruffs, Dummy is high (draw trumps and claim)  


so West has to pitch another heart. 
Now we have won 10 tricks (3 diamonds,  3 clubs, 2 club ruffs and 2 trumps) 
and still have AS and AH in dummy for  12 tricks.      




Michael