update (10 Nov 2014): Zimbabwe and Zambia are going to introduce the so-called "Kaza uni-visa" on 28 November 2014. It will cost $50 and it will be bought at the tourist's point of entry. The visa, which is in its pilot phase, will last for 30 days.
update (23 Oct 2014): According to Tourism Update, the uni-visa for Zimbabwe and Zambia is still subject to cabinet approval. In a news update, Tourism Update quotes an official from the Zambia Department of Immigration saying that a "tentative" date had been set for November 28 but that it would definitely not be launched before then. We'll keep you posted!
The governments of Zimbabwe and Zambia will launch an uni-visa regime between the two countries at the World Travel Market (03-06 Novemer 2014) in London. The two countries expect that the implementation of the joint visa offers the opportunity to market shared national heritage (such as the Victoria Falls) and that it will boost tourist arrivals. We'll keep you posted!