Zimbabwe is a very very different situation to what's going on in Libya. I'll do my best to keep this short.
Things have been improving steadily in terms of quality of life since April 2009 when the US dollar was introduced. People want stability, not more unrest. Right now, they have it, of sorts.
There is a coalition government and the leader of the opposition MDC-T (Tsvangirai) is now the prime minister. There is no call from the main opposition party for intervention.
Mugabe won the 2008 election. He may have won it unfairly (Tsangirai actually got more votes, but not by much). Then the MDC pulled out of the run-off. So he's democratically elected, for better or worse. (Much worse, but anyway.)
Because the election was so close - 48% MDC to 43% Mugabe, you can see that there is still quite a lot of support for ZANU-PF. God knows why, but there is. If you go and try to bring about regime change, you are basically disenfranchising half the population. It could get really messy.
Political violence in Zimbabwe goes in cycles, round election time. It hasn't gone away, but it's far reduced from what it was. Mugabe is not massacring his own people, or about to.
The Daily News - the main newspaper rival to the state-owned Herald, is no longer banned and is freely available. It is frequently critical of the government and provides a much needed outlet for political grievances.
Many African leaders feel a sense of solidarity with Mugabe due to his independence-era background. They will never support his removal as too many of them know they could be next. Skeletons in closets etc.
Any international attempt to remove Mugabe by force would play straight into his hands as he has long sought to portray his own failings as a colonial plot by Britain. The entire SADC community would oppose any external attempt to depose him.
Mugabe is a figurehead. Behind him, and running the country unofficially, is the Joint Operations Command - a group of senior army officers whose loyalty was bought by lucrative Congolese diamond mining deals. If Mugabe goes, they will take over.
The JOC have been implicated in war crimes in the Congo and Matabeleland in the 80s. They have seen what happened to Charles Taylor and none of them fancy appearing in the dock at the Hague. In Africa if you lose power you lose everything. They will have no compunction in launching a civil war, probably with an ethnic or tribal dimension. Nobody wants that.
...So really, very different circumstances and not at all feasible. Let's leave Zimbabwe out of this one.