I don't see any evidence that Ukraine isn't still corrupt since 2015.
And yet, even with your standard of evidence (see below), you were only able to back up the fact that the situation was improving. Curious.
Here is a quote from Zelensky from this year
Just a quick source check for you on that one - the "quote" comes from a personal blog of Iain Muir, proud holder of the title of "some guy on the Internet" and a $5/mo. domain. Some quick research suggests that his greatest achievement in life was an assault conviction, which he appealed in 1999 and failed.
In short, I question this man's blog as a reputable source of Zelensky quotes.