Volodymyr Zelenskyy - why two y's?
His last name contains a common adjective-forming suffix in the Slavic languages. In those langs traditionally written in the Roman alphabet, it is -ski or -sky, while the Cyrillic-alphabet versions are transcribed in several ways. The most common way is -sky, though I've seen -ski, -skiy, -skii, -skij, -skyi, and -skyj. In "Intelligent Life in the Universe" (1964), coauthor Iosif Shklovsky used "Shklovskii". His other coauthor was Carl Sagan.
Reconstruction: Proto-Slavic/-ьskъ - Wiktionary (-isku) has the forms on the attested Slavic languages, along with the Proto-Slavic reconstruction *-isku
With the Baltic langs, we get
Reconstruction: Proto-Balto-Slavic/-iškas - Wiktionary *-ishkas
Its Greek cognate is
-ίσκος - Wiktionary -iskos
In the Germanic langs, we get
Reconstruction: Proto-Germanic/-iskaz - Wiktionary *-iskaz with descendants Old English -isc, English -ish, Dutch -s, German -isch, Icelandic -(i)skur, Danish, Norwegian, Swedish -(i)sk
Going even further gets us
Reconstruction: Proto-Indo-European/-iskos - Wiktionary
That bit aside, there are various sound shifts between Russian and Ukrainian that show up in versions of city names, like Kharkov ~ Kharkiv, Lvov ~ Lviv, and Lugansk ~ Luhansk. Another spelling shift is Odessa ~ Odesa.