You are completely right, when we visited Zimbabwe in 2006 most places accepted US$ or our South African Rand ZAR, it was only the small local shops that had been restricted to using the then Zimbabwe Dollars.

Buying food meant converting to Zim Dollars, at the tills you had one person checking the food out, another sat next to him/her with a special counting machine to make sure the correct amount was paid, a counting machine was needed since it ran into exceptionally high numbers.