I am sorry to say this but past the end of the Cold War I just dont see any ZANU-PF government in Zimbabwe, with or without Mugabe that could lead to continued economic prosperity as opposed to what happened in OTL.
However if without Mugabe, democracy survived in Zimbabwe and not the farce it has become, then some help is at hand.
However the very fact that Zimbabwe is in the mess it is in OTL, is that at the end of the Cold War, they lost a lot of Commonwealth and US support that it got just for being not communist. Where as in South Africa this saw the end of apartheid, in Zimbabwe the end of the Cold War saw the first signs of economic trouble in what was once, one of the richest African nations.
With the continuance of this economic downturn, Zimbabwe then started such grand government schemes as the takeover of white-owned land and the fact that the government printing presses just keep printing more money with more and more zeros on it (I think Zimbabwe is on something like its third currency issue in the last ten years now)
These problems, while not exaberated by erronous Mugabe policies would still take affect to some degree, especially if a ZANU-PF man remained at the helm.