American born Zak made his senior debut for Liverpool against Millwall in the Carling Cup tie at The Den during the 2004/5 campaign.
However, the promising 25-year-old was finding it difficult to establish himself as a regular in the first team set-up at Anfield and jumped at the chance of a loan move to The Den, with the prospect of playing Championship football.
He made an immediate impact in the home game against Leeds United on 26th November 2005, and was virtually ever present thereafter, extending his loan period until the end of the season.
Zak is comfortable on the ball as well as strong in the tackle, and he has all the attributes to forge a successful career in the game.
Everyone at Millwall was delighted when he elected to move to The Den in June 2006. Unfortunately an injury sustained in the home game with Northampton in September kept the young defender sidelined for the rest of the season.
Zak won his fitness battle after a lengthy absence, and following injury to Richard Shaw in November 2007 established himself as the number one partner for skipper Paul Robinson at the heart of the defence. As such, by the start of the 2009/10 campaign, he had made 117 appearances for The Lions.

Previous club: Liverpool
Lions debut: v Leeds United (H) 26th November 2005