Our Zimbabwe plans run on Econet 4G. Econet is the country's largest network, with over 70% of mobile subscriptions, covering Harare, Bulawayo, Mutare and the tourist corridor around Victoria Falls, along with the main highways between them.
Coverage in the national parks is a different story. Hwange, Mana Pools and the more remote parts of Matabeleland have long stretches with no signal at all, so ask your lodge what connection it offers. Plan for offline days rather than expecting a signal in the bush.
Victoria Falls town itself is well covered, including the area around the falls and the bridge. If you cross to the Zambian side at Livingstone, that is a different country and a different plan, so check before you walk over.