The Black Caps completed two embarrassingly easy wins in the Tests, which lasted just two and three days respectively. However, Astle believes Zimbabwe, who have suffered as much off the field with contract and selection disputes as they have on it in the past year, should retain their top-tier standing.
"New Zealand has gone through tough times, Sri Lanka went through tough times and so did Bangladesh."
"Obviously you've got to learn against the better teams in the world. If you drop them out of it, they are going to play weaker teams and not get any better," Astle told The Press newspaper.
"They just have to take what they can out of it."
Astle hit his 15th One-day century for the Black Caps in the tri-series final against India propelling him into the world's top-10 of One-day century-makers alongside Sachin Tendulkar, Brian Lara and Sanath Jayasuriya.
"Any tour when you score two hundreds, one in a test and one in a One-dayer, has to be pleasing."