President of baseball operations Andrew Friedman announced the two hirings in a press release. Here is a quote of Friedman's (via MLBTR.com):
"It is very exciting for us to be able to add two exceptional, veteran baseball executives like Farhan and Josh...Farhan’s primary focus will be the Major League team and player acquisitions while Josh will concentrate on the oversight of scouting and player development. However, they will both work closely with me on all aspects of baseball operations in our efforts to make the Dodgers' front office and team the best it can possibly be."
While at Berkeley, Zaidi read the book Moneyball, which highlights the analytics of the Oakland Athletics front office department. He saw a job posting for a baseball operations job with the Athletics and applied, beating out over 1,000 other applicants for the job. Billy Beane called Zaidi "absolutely brilliant" and credited him with the signing of Cuban outfielder Yoenis Cespedes (who is now with Boston).
Zaidi became the Director of Baseball Operations for the Athletics' front office prior to the 2013 season. In 2014, he became an assistant general manager.
Andrew Friedman, one of the best sabermetric minds in baseball, has completely changed the Dodgers front office since being hired from the Rays early into the offseason. Friedman removed GM Ned Colletti, who is still with the team, and has slowly begun to transform Los Angeles' front office from one that throws money at big free agents to one that will use metrics to determine acquisitions. The hiring of Zaidi is just one of the ways that he shows this.