During his first season in the Alkmaarderhout, De Zeeuw played 26 matches.
Consequently, in May 2006 he was offered a new contract by AZ until 2010.
The following season, he played so well for AZ that he was able to make his debut for the Netherlands national football team under then-manager Marco van Basten.
His contract with AZ was extended again on May 2007.
In the 2007–08 season, AZ performed below all expectations: before the start of the competition the team was seen as one of the challengers for the title, but halfway through the seasons all hope for winning the title was gone.
De Zeeuw described the season as "one giant disappointment".
Manager Van Gaal thought that the role of De Zeeuw in the squad had to change; he had to start carrying the team more.
AZ finished the season in a disappointing 11th position in the league.

After UEFA Euro 2008, De Zeeuw was linked with a move to AFC Ajax where former Netherlands manager Marco van Basten had taken over, but a move failed to materialise.
Partly because of his public soliciting for a transfer he saw himself out of the starting line-up at the beginning of the 2008–09 season in the opening match against NAC Breda.
The player was almost transferred to Hamburger SV on the last day of the transfer period after an accord on the transfer fee was reached between the two clubs.
However the German club was too late to register the player with the German Football Association, so a move again failed to materialise.
Despite his problems at the beginning of the season, De Zeeuw soon fought himself back into the starting line-up during the third league match, a 1–0 victory over PSV Eindhoven.
AZ would not lose a single match in the rest of the first half of the competition, and during the winter break HSV again wanted to sign the player, but AZ stated that they would not allow the player to leave halfway throughout the season.

In the spring of 2009, AZ offered De Zeeuw a contract extension again, this time until 2011.
This time, however, the player rejected the proposal.
At the end of the season, the player celebrated the first championship victory with AZ in 28 years.
The success brought more attention from international clubs including HSV once again.
In July 2009 Ajax officially announced that they were interested in signing the player.
De Zeeuw himself stated that he was interested in moving to the Amsterdam club where former HSV manager Martin Jol had taken over from Van Basten.
AZ initially stated that they did not wish to sell the player to a club they saw as a direct competitor, but after several weeks showed a willingness to cooperate on the transfer.
On 24 July 2009, the definite transfer from AZ to Ajax was announced for a reported €6 million.
The player signed a contract for 4 seasons, until 2013.
During his first season in the Alkmaarderhout, De Zeeuw played 26 matches. Consequently, in May 2006 he was offered a new contract by AZ until 2010. The following season, he played so well for AZ that he was able to make his debut for the Netherlands national football team under then-manager Marco van Basten. His contract with AZ was extended again on May 2007. In the 2007–08 season, AZ performed below all expectations: before the start of the competition the team was seen as one of the challengers for the title, but halfway through the seasons all hope for winning the title was gone. De Zeeuw described the season as "one giant disappointment". Manager Van Gaal thought that the role of De Zeeuw in the squad had to change; he had to start carrying the team more. AZ finished the season in a disappointing 11th position in the league.
After UEFA Euro 2008, De Zeeuw was linked with a move to AFC Ajax where former Netherlands manager Marco van Basten had taken over, but a move failed to materialise. Partly because of his public soliciting for a transfer he saw himself out of the starting line-up at the beginning of the 2008–09 season in the opening match against NAC Breda. The player was almost transferred to Hamburger SV on the last day of the transfer period after an accord on the transfer fee was reached between the two clubs. However the German club was too late to register the player with the German Football Association, so a move again failed to materialise. Despite his problems at the beginning of the season, De Zeeuw soon fought himself back into the starting line-up during the third league match, a 1–0 victory over PSV Eindhoven. AZ would not lose a single match in the rest of the first half of the competition, and during the winter break HSV again wanted to sign the player, but AZ stated that they would not allow the player to leave halfway throughout the season.
In the spring of 2009, AZ offered De Zeeuw a contract extension again, this time until 2011. This time, however, the player rejected the proposal. At the end of the season, the player celebrated the first championship victory with AZ in 28 years. The success brought more attention from international clubs including HSV once again. In July 2009 Ajax officially announced that they were interested in signing the player. De Zeeuw himself stated that he was interested in moving to the Amsterdam club where former HSV manager Martin Jol had taken over from Van Basten. AZ initially stated that they did not wish to sell the player to a club they saw as a direct competitor, but after several weeks showed a willingness to cooperate on the transfer. On 24 July 2009, the definite transfer from AZ to Ajax was announced for a reported €6 million. The player signed a contract for 4 seasons, until 2013.
Demy de Zeeuw