Despite hailing from New England, she insists that she feels 'a bit British'. She seems at home in more ways than one, posing regally for PRWeek's photographer on the manicured lawn of private members' club Home House where, in lieu of a central London office, she does much of her business. Clients include the British Film Institute, for which Martin has been briefed to attract more diverse role models.
Martin launched Acknowledge in 2005 to add some diversity to the 'shockingly homogenous' UK PR industry. She is keen not to be pigeonholed – 'I don't want people to be like, "Oh, that's Zena, the diversity woman''' – but it is an issue to which she is fully committed. As well as running Acknowledge, Martin is a member of the CIPR's diversity board.
Martin has been based in London since she became restless in New York, put everything in storage and abandoned her advertising career, crossing the pond with no work permit and no job. Seven years on, she enjoys dual citizenship and a home in Primrose Hill.
This week, the Commission for Racial Equality unveils its revised Code of Practice for Racial Equality in Employment – a fresh push for employers to actively ensure they have equal opportunities policies.
It is likely to prove a contentious issue for the PR industry. Although the CIPR's most recent survey suggested that 6.5 per cent of the industry had an ethnic minority background, Martin argues that the presence of ethnic minorities at senior level is 'almost non-existent'.
Increasing diversity is critical, she maintains, 'not because we should, or because it would be nice – this is about making money'.
She adds: 'If you look at an American magazine that's marketed to black women, you see major global brands advertising. But when you look at the equivalent in the UK, you see ads from local councils.'
In the US, she notes, WPP owns four marcoms agencies specialising in diversity, including UniWorld Group – founded 35 years ago – where Martin worked in the early 1990s.
'They would not do that unless there were a business case for it. But when I moved here – and London is more diverse even than New York – I was surprised to see that nobody was really doing it. In the States, H&K has had a diversity division since 1987.'
Martin's first job in London was in technology PR for Text 100 during the dotcom boom, after which she headed Firefly Communications' Paris office. Next she launched WPP agency Blanc & Otus in the UK, and later moved to head its sister consumer shop piranhaKid.
Sally Costerton – the incoming UK CEO of Hill & Knowlton – describes Martin as 'an amazing woman with huge energy who invests a lot of her time in her staff'.
Indeed, while Martin is reluctant to blow her own trumpet ('uh... people say I'm a really good cook'), her energy is palpable. She packs in a healthy social life with plenty of charity work: 'If you feel complacent, like you have done it all, what's the point of getting out of bed in the morning? I want to constantly evolve until I keel over.'
And she admits that there is much work to do. While it is crucial that PR represents its customer base, few ethnic minorities consider it as a career. 'I don't think companies are trying hard enough,' she says. 'They have to be creative and committed. Get the recruits younger – create internship programmes, encourage them to take PR courses. Show them the benefits of a career in PR.'
However, preferential treatment is the last thing Martin wants: 'This is about business. The market is there. I would never want someone to hire me because I tick some box. Hire me because I'm good, and then it's a bonus that I happen to be from an ethnic minority.'