ZenithOptimedia is The ROI Agency, part of Publicis Groupe, offering media services from 250 offices in 74 countries with over 6.000 staff worldwide and more digital staff than any other agency.
There are a number of divisions within the ZenithOptimedia Group – Zenith and Optimedia, plus Newcast (non-traditional solutions), Ninah (econometrics), Meridian (OOH) and Performics (performance marketing).
http://www.zenithoptimedia.com

Publicis Groupe is present in 104 countries and through employing 58,000 professionals it is the third largest communications group in the world. Publicis Groupe is listed on the Euronext Paris [FR0000130577] and is part of the CAC 40 index.
The Groupe offers the full range of services: digital (DigitasLBi, Razorfish, Rosetta, VivaKi), traditional advertising (BBH, Leo Burnett, Publicis Worldwide, Saatchi & Saatchi), public affairs, corporate communications and events (MSLGROUP), media buying and strategy (Starcom MediaVest Group and ZenithOptimedia) and healthcare communications, with Publicis Healthcare Communications Group (PHCG).
http://www.publicisgroupe.com/