While many of Zimbabwe's highlights can be accessed by travellers with restricted mobility, it's definitely recommended to travel with the assistance of a companion. In the larger towns and national parks, there's usually a few hotels or lodges that can cater to travellers in wheelchairs.
Though safari vehicles in the parks aren't set up for wheelchair access, travellers can be hoisted into the car with help. The paths leading to outlooks of Victoria Falls are fairly navigable. For the most part, though, when getting around towns and rural areas you'll encounter some uneven surfaces.