I want to concur with the (IMHO) important question.....
Where are South Africa and the neighbor states. Zimbabwe, according to all blog pundits has a seasoned and well-trained military. (Haven't we heard that before? Just wait 'til they try to take Baghdad! Then they'll be up against the crack troops of the Revolutionary Guard.) From everything I've seen, the Zimbabwean military excels at encircling motorcades of journalists and visitors, burning out squatters, and beating up political opponents and their supporters.
What would be required, unfortunately, would be getting Angola, Zambia, and Mozambique to sit at a table and actually agree to something for a change (with South Africa, of course).
No amount of condemnation in the parliaments of Europe or North America is going to do anything if it's not backed up, and there's no way that any of those countries, nor the UN, are going to sanction any military action against a land-locked African country without support from at lest two of the border states.
There are a lot of African leaders, though, who don't want to do a thing. Oppressive regimes have been commonplace on the continent, and they always come and go. Besides, any form of a three or four country alliance to force a settlement on another state makes them nervous. Every country has three to five neighbors, and they don't want the precedent to be set. You could be next year's Mugabe, after all.