W----N----E----S -----1D---/----1H /----1S---/----2D* /----3D---/--- /----3S---/----3NT /----4D---/----4NT /----5H--/-----6H // 2D = X-Y-Z, FG S: KJ73 H: K4 D: AKQ94 C: 85 S: 8 H: AQ9862 D: 87 C: AQJ3 Lead=SA, then the defender pitches a low Heart. Please try to avoid the Club loser. Since we've already lost to SA, the H must break (32). Thus, we should have 1S+6H+3D+1C = 11 tricks. Don't forget that we cannot establish the D suit via ruffing because there is no entry to the dummy other than D after we've drawn all the trumps. The CAQJ3 in your hand is the problem, and two of the Clubs can be discarded by SK and DQ so this contract is only related to CQ.
From a single suit perspective, the CQ problem can be solved by: Directly finesse the CQ and D 3-3 break.
The first extra possibility you may think of should be someone holding 3-card Spades with Q, by ruffing a Spade we can set up the SJ. Thus, the general sequence we can do is: HA HK -> S ruff (try to set up the Q) -> HQ (draw all the trumps, discard a C in dummy) -> DA (enter the dummy) -> SK (hoping SQ knocked out, discarding C3) -> DK DQ (hoping D 3-3)-> C to CQ (finesse). Then we can make some improvements on this deal, by imaging West holding all the guards to S (AQxx+), D (4+-card with DJ or D10) and C (CKx). S: KJ73 H: K4 D: AKQ94 S: AQxx C: 85 H: xx D: J10xx C: Kxx S: 8 H: AQ9862 D: 87 C: AQJ3 On the third round of H, West is forced to discard a C otherwise this contract (otherwise we can set up the D suit or SJ). Then what's next? Continue a H, discarding a D in the dummy (be in mind we only want 1 more trick), West will be in trouble. This is called a triple squeeze. Besides, we can also success in similar cases: S: KJ73 H: K4 D: AKQ94 S: Axx C: 85 S: Qxxxx H: xx H: xxx D: J10xx D: xx C: Kxxx S: 8 C: xxx H: AQ9862 D: 87 C: AQJ3 HA HK -> S ruff (try to set up the Q) -> HQ (draw all the trumps) -> DA (enter the dummy) -> SK (hoping SQ knocked out, discarding C3). Then if we change our plays a little bit by then ruffing the SJ, what's next? (West has to discard his Clubs for the same reason). S: ---- H: ---- D: KQ94 S: ---- C: 8 S: x H: ---- H: xxx D: J10x D: xx C: Kx S: ---- C: xxx H: 9 D: 8 C: AQJ Then if we continue play the H9, West will be in trouble again. This is called a simple squeeze. Please notice that his best defense is to discard a club, holding singleton CK. Then we should guess whether to knock down his CK or still take our finesse. However, from the previous play his distribution will be exposed into 3-2-4-4, thus the probability he is holding CK is 4/7. Also, if you observed West feeling ill and difficult to discard, he is likely squeezed.