Los Che move closer to European glory with an impressive victory over the Dutch side, who disappointed after winning the first leg in Netherlands
Adil Rami brought the hosts level overall after only 15 minutes, with a header from a corner, doubling his tally only two minutes later with a volley.
Jordi Alba tapped home ten minutes after half-time to make it three, and Pablo Hernandez curled in with ten minutes from time.
The game started with a bang, with Los Che providing the early pressure. They knew they needed at least one goal, and were seeking it early on, looking most dangerous from set pieces.
Indeed, it was a corner that led to the first goal. On the quarter-hour mark Tino Costa passed to Sofiane Feghouli, who crossed from the right for Rami to emphatically head home, with Esteban Alvarado missing his punch.
Just two minutes later, it was Rami that put the hosts two up, and ahead on aggregate from another corner. Tino Costa crossed in after another short corner, the ball was flicked on, and the former Lille man was there at the back post to sweep in a volley.
The Dutch side were looking shell-shocked, but they did muster an effort on target. Adam Maher with a speculative first time shot from distance, Diego Alves doing well to claw the ball over the bar.
Just before half-time, Unai Emery's side almost extended their advantage as Jonas slipped Roberto Soldado through, only for Esteban to save the Spaniard's effort. The ball was whipped back into the box, but Jonas headed just wide of the left-hand post.
AZ came out in the second-half knowing a goal would make sure the tie went to extra-time, but they soon fell even further behind.
Dirk Marcellis blocked a shot on the line, and in the ensuing melee Nick Viergever was dispossessed, and Soldado squared the ball to Alba, who poked home on 56 minutes.
Valencia were loooking comfortable, and they made the victory a certainty when Alba swept in a cross from the left into the path of Pablo in the box, who curled the ball into the top right-hand corner of the goal.
Unai Emery’s side are into the semi-finals of the competition for the first time since 2004, when they won the trophy, while Gertjan Verbeek’s team can be satisfied with their efforts, being the only Dutch team to reach this stage this season.