The two shorter-form games were won comfortably on the back of strong form from McCullum and Martin Guptill; the first two ODIs went the same way, Rob Nicol showing his credentials with a century at the top of the order, while Zimbabwe chased down 329 to win the third by one wicket in the final over.
Selections are wide open, with several contenders putting a solid case over the past few weeks.
First the T20.
It may be a shade uncharitable to say so, but the selectors might figure that Zimbabwe is the right time to take a look at a couple of new faces, with South Africa having three T20s when they arrive next month, and two in the Caribbean mid-year before the world T20 in Sri Lanka.
Some of those on the Zimbabwe tour won't be seen this time around, but the selection is also related to how much the selectors work with HRV Cup form.
If they do, then Auckland left-arm spinner Ronnie Hira should be in the squad. He topped the competition with 14 wickets at 14.85 and was an essential part in Auckland's successful title defence.
So too James Franklin, whose T20 numbers impress, and a case can be made for retaining his Wellington team mate, left-arm quick Andy McKay, whose 12 wickets at 19.83 enable him to put his hand up. Not to forget young speedster Adam Milne, who had a brief taste last season, and is looking lively. His 11 HRV Cup wickets for Central Districts were achieved at the highly competitive strike rate of 13 balls per wicket.
Another batting option is now needed. Canterbury's Tom Latham hit a brisk 130 against Wellington on Thursday. Give youth a chance?
Veteran allrounder Jacob Oram, albeit short on recent matchplay, comes back into the frame, more so for his bowling these days, and the selectors should look at a lower-middle order hitter. On form, none appeals more than Auckland's Colin de Grandhomme or Canterbury's Andrew Ellis, both uncapped.
There will be a desire to keep players in the fold, so Wellington spinner Luke Woodcock, who has performed well, will be considered.
McCullum keeps in the shorter forms, but there will be a desire to retain Watling, given that he's their new test man and needs as much time behind the stumps as possible.
The first ODI against Zimbabwe is in Dunedin on Friday.
ODI
Possible New Zealand ODI squad
Brendon McCullum (c), Martin Guptill, Rob Nicol, Kane Williamson, BJ Watling, Dean Brownlie, James Franklin, Nathan McCullum, Luke Woodcock, Jacob Oram, Doug Bracewell, Tim Southee, Kyle Mills, Andy McKay.
T2O
Possible New Zealand T20 squad
Brendon McCullum (c), Martin Guptill, Rob Nicol, James Franklin, BJ Watling, Tom Latham, Colin de Grandhomme, Nathan McCullum, Ronnie Hira, Jacob Oram, Doug Bracewell, Tim Southee, Kyle Mills, Adam Milne.
