I know in the west we heard about Zelensky's millions with the release of the Panama Papers, but I don't know how widely it was known in Ukraine.

Yes, he did. He tried. Then he gave up and apparently decided, "If you can't beat 'em, join 'em."

The link below contains quotes and links for the information you asked about.

qhttps://xenagoguevicene.wordpress.com/2022/03/05/ukraine-zelensky-and-the-fascists-he-will-hang-on-some-tree-on-kreshchatyk-by-moon-of-alabama-5-march-2022/

A great general source is "Moon of Alabama."

https://www.moonofalabama.org/