Is your uncle John SIKORSKI the one born in Oct 1858 and is found in 1900 in Hibbing, and in 1910 in Virginia, St. Louis County? That John appears to be my Zenon's (1873-1934) brother.
So, no, I don't believe Zenon is Polish for "John" (that I believe should be "Jan"). The nearest I can find is that Zenon has Greek roots. I'm not sure how my grandfather came by the name. Zenon and this John's parents were Frank and Amelia (SKROCKA) SIKORSKI.