CHICAGO (AdAge.com) -- Mazda has cut Doner from its ongoing agency review, ending a relationship that dates to 1997 and yielded the carmaker's signature "Zoom-Zoom" tagline.

"It's with a heavy heart and great disappointment that we must share the news that Mazda has decided to go in a new direction," Doner said in a memo circulated to staff this morning. "While we fought valiantly throughout the process and laid it all on the line, Mazda has decided to move on. And so must we."

The cut leaves a hybrid team from WPP, Omnicom Group's DDB and MDC's Crispin Porter & Bogusky in the mix for the account. Executives at those agencies said they were told to expect word on next steps this week. Mazda spent $152 million on measured media in the U.S. last year, according to Kantar Media, though its spending has typically exceeded $200 million in the past.

WPP, which handles Mazda's business in much of the world outside of North America, is regarded as a favorite in the review, which began in early March. At the time, a Mazda executive said the company wanted to be sure it was getting "the best work and the best price."

For Doner, however, it's a cruel blow -- and not only because the client intends to continue using its "Zoom-Zoom" tagline with its new agency.

Winning Mazda in 1997 in a pitch that also included GSD&M and Ogilvy & Mather was the exclamation point on the independent's transformation from a strong, regional independent into a national force. It also greatly increased the agency's footprint, as Doner opened an Irvine, Calif., branch to work on Mazda.

In the memo this morning, Doner touted the results from its work for Mazda: "Together, with many supportive partners at Mazda North America, we generated outstanding results: we invented 'Zoom-Zoom,' an emotional, differentiating and remarkably memorable brand platform that will remain the foundation for Mazda's global marketing vision into the next decade; we accelerated Mazda's use of the digital space with highly innovative digital programs like the '33 Keys' alternate reality game; we re-ignited confidence, support and passion for the brand among dealers across North America; we successfully launched the brand in Mexico; and, most importantly, over the past 10 years, we have helped Mazda grow its share in Canada from 2%-5.5%, in Mexico from 0%-3.3% and in the U.S. from 1.4%-2.0% with Mazda achieving its highest U.S. retail market share in over 10 years in March 2010."

Today, Mazda is the agency's largest account, accounting for about 20% of revenue, according to Doner executives.

That won't be easily replaced, although the agency has won a series of smaller accounts of late, including Wilson Tennis, Avery Dennison office supplies and project work for Experian Consumer Direct. It also still works for major marketers such as Coca-Cola (on Minute Maid), Coleman Co. and the Del Taco restaurant chain.

Doner, which was sold by former CEO Alan Kalter late last year to former Chief Operating Officer David DeMuth, Chief Creative Officer Rob Strasberg and President Tim Blett, has also been in the process of attempting to change its perception as a TV-centric agency best known for campaigns such as Six Flags' "Mr. Six" to a shop more synonymous with digital and nontraditional campaigns under the guidance of Mr. Strasberg, a Crispin Porter alum.

Executives point to an alternate-reality game for Mazda Canada, a fantastical cardboard world created for the UPS Store and online-video and social-media driven efforts for Del Taco as evidence that this is a "new Doner." And they've also changed the agency's website and logo.

But it's safe to say that losing Mazda wasn't the sort of change the agency was looking for. "While the sting of this loss is painful it's one that will pass quickly," the executives wrote. "Our sights are already set on the future and our new business initiative is focused on winning a new automotive account as well as other exciting opportunities in the pipeline."