The story of Zacchaeus is rich in possible interpretations.
The most popular interpretation is to view the story in terms of conversion. Here is a rich man who has not cared for the victims of poverty and injustice until his encounter with Jesus. His conversion makes a strong statement about the affluent caring for the needs of the poor.
It has also been suggested that what changed in Zacchaeus was his concern for those whom he had defrauded. He had always been generous with the poor, but now he cared about all the oppressed. In other words, his growth was from charity to justice.
Recent biblical scholarship has tended to view the story more in terms of the vindication of a person whom society considered a sinner. Everyone thought Zacchaeus was a terrible person because he collaborated, as a tax collector, with the hated occupiers. Jesus unveiled the truth about the man, who in reality was concerned for the welfare of others. The judgmental world was once again proven wrong.
Take your pick! The interpretation of your choice has enormous implications for the pursuit of a better world.
It is the duty of the whole People of God … to alleviate as far as they are able the sufferings of the modern age. They should do this … out of the substance of their goods, and not only out of what is superfluous.
Vatican II, Constitution on the Church in the Modern World, 1965: 88