Here goes, but this is my view only.
Europe, or to put it another way, the white races, have, as you know, a colonial history in Africa, and if they interfere, the cry of Colonial interfereing will go up, even if they were to 'invade' alongside a black nation, and as such, I believe, can do hardly anything at all.
Mbeki is the only political leader who can do something, I don't think there's another African nation powerful enough, but thats not likely if this is true.
http://www.thetimes.co.za/PrintEdition/News/Ar ticle.aspx?id=792739
Something Europeans can do, is to stop buying Zimbabwean produce, its that money thats helping to keep mugabe afloat, but other than that, unless they grow another pair of
cojones each, there not much will happen.