I've seen his first name spelled: Sergi, Sergei, and Sergiy.I've seen his last name spelled: Dzindziruk, Dzinziruk.So, what is it really?
There is no "correct" answer. Ukrainian names always wind up having multiple possible transliterations from the Cyrillic alphabet into the Roman alphabet we use in English. For instance, did you know that "Wladimir Klitschko" is not necessarily correct? Some linguists would in fact consider it expressly incorrect, and tell you that Volodymyr Klychko is right. I've heard it said that "Wladimir Klitschko" is a Russianized or Germanized version of his real name. This kind of confusion happens with most Ukrainian fighters (Wladimir Sidorenko/Volodymyr Sydorenko, Andreas/Andrey/Andriy Kotelnik etc.), whose names for whatever reason undergo a more difficult transition into English than other Slavic peoples.
It is definitively incorrect. Володимир/Volodymyr his Ukrainian name Владимир/Vladimir is the Russian version of the name Wladimir is a German spelling of the Russian version. Sergei, Sergiy can be spelt multiple ways all of which are fine. Dzinziruk like you have is correct. It's because of the Cyrillic into Roman/Latin alphabet conversion. Some of the Cyrillic letters and sounds don't exist in the other alphabet.
Whatever his name, he's one hell of a fighter and I'm looking forward to tonight! Go Sergiy... Sergi... Whatever! :bbb
The "correct" version (for you) depends on where you live or what language you speak. There are different official transcription of cyrillic names for different languages.
His last time is difficult for even Ukrainians to spell because "Dzinzi" is not a very common sound in this language.
Not exactly, I'm not making light of the situation, but it's a word that commonly has two different spellings depending on if you're using Russian or Ukrainian transliteration.
Actually Wladimir´s name is correctly pronounced as Vladiimir. (Not that you have two i´s in it but you pronounce it that way)