By 'in Zim', do you mean hosted in Zim or developed in Zim?
Anyways here's a list of sites accessible to Zimbos
e.g. Facebook, Google Plus
Get featured on zim blogs or better, do your own blog and promote the stuff yourself.
e.g. Google Adwords and other advertising platforms
A holistic approach covering all of these platforms will achieve better results. Look at your target market, which sites do they visit often? How do they use the internet (mobile/desktop) etc and then strategise.
Remember (as an overly simplified example), people do not type in "amazon.com/buy/red-honda-scooter" rather, they google "red honda scooter" and then take it from there.