It sometimes shows some surprises, just like weak teams do, Zimbabwe sometimes shows such surprises. As far as I know, Zimbabwe will not be able to win a single match in this tri-series because before this series started, there was a series between Zimbabwe and South Africa but Zimbabwe lost all the matches there. It is a tri-series where New Zealand is definitely a first-class team and comparing Zimbabwe with New Zealand and South Africa is really unfair/unrealistic. I am speaking based on current performance.
You are very realistic about Zimbabwe chances in this tri series and it is hard to disagree. Their recent losses to South Africa show clear difference in skill compared to top teams, so even though weak teams sometimes surprise and I also do not expect it from Zimbabwe here just like you. You pointed out that it is just not fair to compare Zimbabwe to strong teams like New Zealand and South Africa given their current performance making it very tough for them to even win single match. Your prediction based on recent results and opponent strength makes much of sense.