Defeats in either test at the Queens Sports Club would be a devastating start to the post-Brendon McCullum era.
The last time the venue was used for a test, in November 2011, New Zealand edged to victory by 34 runs as Zimbabwe faltered in a chase for 366. Zimbabwe, mentored by former Proteas Makhaya Ntini and Lance Klusener, have not played a test since November 2014. They are playing South Africa A to prepare for the series. The first match in Harare was drawn; the visitors are dominating the second at Bulawayo.
The New Zealanders are also scrutinising the social landscape, with Zimbabwe facing a debilitating drought and economic paralysis.
Jobs are scarce, wages are restricted and money can't be withdrawn from banks. Violence marred a strike last week. Britain's Telegraph newspaper said a warehouse was set alight on the South African border protesting against import restrictions, and bus drivers attacked police in protests against roadblock bribery.
New Zealand Cricket are monitoring South Africa A's tour and getting status updates from the Ministry of Foreign Affairs and Trade and the independent security consultants who did their tour reconnaissance.
The team cannot pull out solely for political reasons, but could exit if their safety and security is deemed to be threatened.
New Zealand defeated Zimbabwe 2-1 in an ODI series last year in which there were no major threats.