Marquis, who is currently chief executive of Zenith Media UK, will oversee the operations of both Optimedia and Zenith as the two agencies pool their media-buying power.
The changes to its media-buying operation come after a hectic week of announcements from Publicis, following the completion of its $3bn (£1.9bn) merger with Bcom3.
Publicis announced that it was to close the D'Arcy advertising agency and merge parts of its business with Leo Burnett and Saatchi & Saatchi, with a new unit being created out of its General Motors business.
The elevation of Marquis will see Tom George, managing partner at Zenith, head up Zenith Optimedia's buying in the UK. He will report to Marquis, who will report to Zenith Optimedia worldwide CEO John Perriss.
The creation of the new roles for Marquis and George will not affect the day-to-day running of the two agencies, which will remain with Zenith managing director Tim Greatrex and Greg Turzynski at Optimedia.
Marquis and George, working with the two managing directors, will be looking for ways in which the two agencies can work more closely together.
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