Both teams still have dreams of reaching next month's showpiece event in Prague against either Basel or Fiorentina, but it is the Hammers who hold the advantage courtesy of their 2-1 first-leg victory at the London Stadium last week.
Match preview
AZ Alkmaar appeared to be in control of the first leg heading into half time, with a long-range effort from Tijani Reijnders putting the possession-hungry visitors in front against a frustrated West Ham side on the 41-minute mark.
However, the tie was turned on its head in the final 25 minutes as a converted penalty kick from Said Benrahma restored parity for the Hammers before Michail Antonio prodded home in the 75th minute to condemn the Dutch outfit to a first-leg loss.
AZ remain firmly in the contest, though, and manager Pascal Jansen is sure to remind his players of their quarter-final triumph over Anderlecht last month in which they bounced back from a 2-0 first-leg defeat to draw level on aggregate before winning 4-1 on penalties in front of their home supporters.
Jansen's side quickly put aside their defeat in the English capital when they secured a thumping 5-1 home victory over FC Emmen in the Eredivisie on Sunday, with Sam Beukema (2), Sven Mijnans, Myron van Brederode and Jordy Clasie all scoring in a first-half onslaught to help the Cheeseheads climb above Ajax into third place with two games remaining.
AZ enter Thursday's second leg with an impressive unbeaten home record in European competition, winning 17 and drawing eight of their last 25 matches, including qualifiers, in Alkmaar, while they have won all eight home games in this season's Europa Conference League by an aggregate score of 25-5.
The Dutch side, who are seeking to reach their first European final in 42 years, also boast a solid home record against English opposition having only lost one of their previous eight such meetings, although that defeat was against an Everton side who were managed by current West Ham boss David Moyes in 2007-08.
Twelve months on from losing their Europa League semi-final to eventual winners Eintracht Frankfurt, West Ham are in the driving seat to reach their first European final since 1976 following a dogged comeback victory in last week's first leg over AZ.
The Hammers are making a name for themselves as comeback specialists having won four ECL matches when conceding the opening goal, beating FCSB, Silkeborg, Gent and now AZ, and they are the only team who are yet to lose in this season's competition, putting together a 13-game unbeaten run.
West Ham, who have progressed from all nine of their previous European knockout ties when winning the first leg, require just a draw on Thursday to reach next month's final, although their form away from home is sure to be a concern for David Moyes as his side have lost six of their last 10 matches on the road in all tournaments, including each of their last three.
The Hammers' latest setback on their travels came against Brentford where they suffered a 2-0 Premier League defeat on Sunday, with first-half goals from Bryan Mbeumo and Yoane Wissa condemning Moyes's much-rotated side to their 19th top-flight defeat of the season.
Unlike AZ, West Ham have endured a disappointing domestic campaign and have been languishing at the wrong end of the table for some time. Despite that, they have all but secured their Premier League status for next season as they sit six points clear of the relegation zone with just two games remaining, meaning the East Londoners can now essentially prioritise their European campaign.
The pressure remains on Moyes's shoulders, though, with the Scotsman tasked with ending the club's 43-year wait for silverware and securing the first trophy of his managerial career, a feat that could potentially save his job in the Hammers hotseat.
AZ Alkmaar Europa Conference League form:
W
W
W
L
W
L
AZ Alkmaar form (all competitions):
W
W
W
D
L
W
West Ham United Europa Conference League form:
W
W
W
D
W
W
West Ham United form (all competitions):
L
L
L
W
W
L
Team News
AZ Alkmaar goalkeeper Sem Westerveld and former Stoke City defender Bruno Martins Indi remain sidelined with respective knee and hip problems, but Dani de Wit and Jesper Karlsson both recovered from injury to feature as substitutes against Emmen and are set to be involved on Thursday.
Pantelis Hatzidiakos is available to return after serving a domestic suspension last weekend and the centre-back will likely replace 18-year-old Wouter Goes in the starting lineup.
Reijnders and Clasie are expected to continue in centre-midfield with Mijnans operating in the number 10 role, while top scorer Vangelis Pavlidis - who has scored five ECL goals in six games - is set to lead the line.
As for West Ham, Antonio and Angelo Ogbonna missed the defeat at Brentford due to respective calf and illness issues, but the pair will likely recover in time to make the matchday squad on Thursday - the former of whom remains in the Golden Boot race having scored six ECL goals in seven matches.
Vladimir Coufal has returned to light training following a spell out with a hamstring injury, but it remains to be seen whether he will return against Alkmaar, so either Ben Johnson or Thilo Kehrer is set to start at right-back. Gianluca Scamacca, meanwhile, is still recovering from knee surgery.
Moyes made nine changes to the side that lost to Brentford on Sunday, resting the likes of Benrahma, Declan Rice, Jarrod Bowen, Lucas Paqueta and Kurt Zouma who are all expected to be recalled to the first XI.
Alphonse Areola was arguably at fault for AZ's opening goal in the first leg, but the Frenchman has been West Ham's cup goalkeeper throughout this season and will continue between the sticks on Thursday at the expense of Lukasz Fabianski.
AZ Alkmaar possible starting lineup:
Ryan; Sugawara, Beukema, Hatzidiakos, M. De Wit; Clasie, Reijnders; Odgaard, Mijnans, Van Brederode; Pavlidis
West Ham United possible starting lineup:
Areola; Kehrer, Zouma, Aguerd, Cresswell; Rice, Soucek; Bowen, Paqueta, Benrahma; Antonio
We say: AZ Alkmaar 2-2 West Ham United (West Ham United to win 4-3 on aggregate)
Fresh from their five-star performance in the Eredivisie last weekend, AZ Alkmaar must continue their clinical form in front of goal if they are to overturn the one-goal deficit in front of a fire-up home crowd on Thursday.