As well as Howley, the agency has promoted Marco Bertozzi, the former commercial director of Zed Media, to marketing director.
Howley will be responsible for a group of 35 planners and will also sit on the management executive board. He will work across the range of Zenith's clients, which include British Airways, Procter & Gamble and Toyota.
Bertozzi's brief is to focus on new business, as well as spearheading the agency’s general marketing requirements.
Gerry Boyle, ZenithOptimedia's managing director, said: "Mark and Marco are both brilliant operators. Their input to different parts of the business will be crucial in helping us fulfil our potential this year."
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