What I'd like is what Marius and Julius Vogel have set out.
Trouble is, IF Mugabe dies ca 1983- IMO you get a bloody civil war within ZANU with 300K dead and 1MM wounded and roughly OTL refugeee population (3-4MM) fleeing the country.
Sure, the economy's a mess and there was a nasty massacre (Gukurahundi campaign from 1982-1985) that killed @ 20,000 Matabele IOTL . IMO, it'd be far worse.
As to the Matabeles, whites and dissident Shona finding common cause---
and cooperating to restrain Mugabe, essentially that's what MDC tried to do, but between ZANU patronage, vote rigging, and downright police repression, it's clear trying to unseat Mugabe's a dead letter through the ballot box.
The sad fact is IF Tsingvarai and MDC actually got power, are there any gurantees it won't just switch who's got the levers of powers and thus who gets the big cut of profits?
Anyone can do anything, given time and the right resources at hand.
Zimbabwe can be a functional democracy with prosperity for all.
The main problem is that the economy's main earners- agriculture and mineral exports are pretty easy to manipulate to the benefit of whomever's in power.
The land "reforms" redistributing land to ZANU supporters have wrought havoc on yields of cash and subsistence crops.
Tourism isn't bad either, but it requires a bit more flexibility than ZANU-PF allowed.
Microcredit and encouragement of entrepreneurial ventures would do wonders to help Zimbabweans improve their own lives and develop their own internal economy.
Trouble is, the folks that have most often made that happen were whites and Asians and that created no small amount of bitterness considering that ZANU-PF stressed the benefits of everyone having roughly the same benefits with nobody being a privileged class except for the leaders of the revolution, of course.
Also, whomever's in charge shouldn't let health care go down the drain during the AIDS pandemic!
Between AIDS and cholera outbreaks, it's obvious nobody's minding or funding the public health.
Do the public education about AIDS, safe sex, condom distribution, and aggressively negotiate for AZT and other drugs to help stop the transmission of AIDS from mothers to infants.
The education and rubbers are cheap.
Cholera's preventable, but when you can only run power three days a week, how do you expect to adequately treat sewage?