It is definitely possible to say that this tax looks absolutely unfair and it is just a way for the state to get rich on the happiness of the winners. At the same time, the state does not care that people spend their money on casinos, no one returns 10 percent to them. If I were a gambler and betting enthusiast from Zimbabwe, I would simply play at those casinos that are associated with cryptocurrencies and which, unlike state casinos, do not transfer data on winners to the state.
Zimbabwe is a third world country and people have been using gambling as mean to become rich. But, If you practically think about it only a few win from gambling not all are lucky. This tax might be a way to stop people from getting poor through gambling and it's addiction. I don't agree with your point of view on government getting rich through 10 percent of winning amount. As, I said earlier only a few will win but a majority will lose.