From the US DoS web-site:

"Zimbabwe offers opportunities for observation of wildlife in its natural habitat. Many tour operators offer structured, safe excursions into parks and other wildlife viewing areas for close observation of flora and fauna. However, even animals marketed as “tame” should be respected as wild animals and travelers should keep a safe distance from animals at all times, remaining in vehicles or other protected enclosures when venturing into game parks. A foreign tourist died in August 2005 after an attack during a “lion walk” at a game preserve near Harare. In 2004, an American tourist was killed by a crocodile while in a canoe at Mana Pools on the Zambezi River. It is a good idea to ascertain whether operators are trained and licensed. However, U.S. citizens participating in nature excursions in Zimbabwe should be aware that even organized and licensed tour operators may encourage or allow tourists to participate in activities that could pose great risks to personal safety."