After a brief search, this appears to be true. With the caveat the ultimate source seems to be Zelensky himself. The articles I surveyed all referenced interviews and speeches of Zelensky.
Honestly, the only part I wouldn't trust is the idea the men willingly joined instead of being drafted. I'm pretty sure most Eastern European men can trace their family back to fighting Nazis, except for the ones who were Nazis.
Yeah... What they tend to leave out is that anywhere from 100-250k people in Ukraine fought with the Nazi, while anywhere from 6-7 million Ukrainians fought against them, and had some of the hardest fighting on the eastern front.