The way I see it, there are 2 very different set of circumstances that cause inflation. One is what people commonly think of, and the old pat answer that it's the printing of money. As I see it, that only happens in pretty extreme circumstances, or economies in which the currency is actually the largest part of the money which is available to be spent. Which is to say, more primative cash economies. People who are one step up from subsistence food production don't have a lot of bank accounts, checking accounts, and credit cards.
The other, in a modern economy with a well developed financial system, cash doesn't matter that much, and it would even be possible to get rid of it altogether. Actual cash shrinks to a tiny percentage of the money supply. By the broad definition of money, cash is less than 5% of the actual money supply, and to print money to cause inflation would be the tail trying to wag the dog. money, at least as far as inflation is concerned, ceases to matter. And what matters is that the supplies and the demands for goods services change over time, but typically go up. When you have a fixed amount of something, and more people want it, then the price of it is bid up. And this is a rolling process through the economy, as the rising price of one thing encourages price increases in other things to compensate for that.
I don't know if Zimbabwe flirted with having a modern economy before Mugabe ruined it, I don't know that much about that nation's history. But it clearly doesn't now. So I think this is a classical situation of inflation is a "monetary phenomena".
As to why it is being done, that's a classic story as well. The economy is in shambles, and the government is paying all it's bills by printing money instead of taxing or borrowing.
The way to stop it is to get a new, revalued, currency and then practice sound fiscal and monetary policies.