Zander, 60, will be replaced by President and Chief Operating Officer Greg Brown, 47, as CEO.
The departure announcement was not unexpected and Motorola shares moved up only slightly in morning trading, reflecting continuing caution on Wall Street toward the Schaumburg, Ill.-based company.
Zander, who will stay on as chairman until the company's annual shareholders meeting in May 2008, maintained that the decision to go was his alone despite the severe criticism he received for the company's struggles over the past year and calls from some shareholders to replace him.
"This is what I wanted to do," he said in an interview with The Associated Press.
"You'd like to leave when you're at the top of your game. ... You don't like to leave when you have a year like this with mobile devices," Zander said. "But I think we have enough structurally done with this company that when mobile devices does get back to its execution, we're a stronger company than we were four years ago."
He said he planned to "go do the things that my wife and I have wanted to do now for years and years."
Banc of America Securities analyst Tim Long called the transition a "slight positive" for Motorola.
"We view the change positively as we believe a fresh strategy may help restore growth and aid a quicker bounceback in operating margins," he said in a note to investors.
But the departure also left some wary about what it might signal about Motorola's nascent turnaround effort.
"While Mr. Zander's departure has been the source of speculation for some time, we had thought that an improvement in mobile devices could possibly grant him a stay," said Citigroup's Jim Suva in a research note. "We now wonder if today's announcement signals yet another disappointment for the handset segment and more meaningful changes that have to occur."
A two-year run of success Motorola enjoyed following the launch of its Razr phone began crumbling last year after sales slowed and the company admitted it had been trading profit margins for global market share by aggressively undercutting pricing.
Motorola has since slipped to third place in the cell phone market behind Samsung Electronics Corp. and remains far behind leader Nokia Corp.
