Mr. Perriss declined comment, referring calls to Publicis' chief operating officer, Roger Haupt. Mr. Haupt wouldn't comment directly on negotiations with Mr. Perriss.
"We are reviewing the best way to move forward with regard to all our media operations," Mr. Haupt said. "We are examining our existing media operations. We have done that with all our operations. We've been looking at how we can best compete to provide the best service to our clients."
It is unclear who his successor will be, though Zenith Optimedia Group's North American CEO, Rich Hamilton, is likely to be a contender.
Mr. Perriss, 56, has long-indicated his desire to swap his current position for a non-executive role in the advertising world. His exit, however, could be related to a previously stated desire by Publicis to link Zenith Optimedia with its other media network, Starcom MediaVest Group. Publicis CEO Maurice Levy in January told Advertising Age of his desire to see some "integration" between the two agencies.
Zenith Optimedia has an estimated $18 billion in global billings Hewlett-Packard, Toyota's Lexus, British Airways, Verizon and S.C. Johnson & Son among its clients. Starcom MediaVest Group has billings estimated at $17.9 billion. The Chicago-based company counts General Motors Corp. and Kellogg among its major accounts.