Hello,
The name of president of the Ukraine is ZELINSKY. 
I personally don't think ZELINSKY and ZELEVANSKY names are related.
AFAIK Zelinsky name origin is Silesia while Zelevansky is Zelva.
Why I know this? Cause I am researching ZELIVIANSKY (rus. Зеливянский) whivh is pretty much same as Zelevansky. It's my maternal grandfather family name.
This family line is originally from Slonim, Belarus.
Let me know if you are interested to discuss.
BR,
Vladimir
NJ