If you want to generally improve as any particular champion, consider looking at pros play them.
There's channels (Lol Pro Replays comes to mind) that exclusively show replays of those champs.
Personally, I love
KZ. His most important factor is his ult.
Are they not grouping up at all? Q. Do they group too much / need to be slowed heavier? W. I need more leap range E. Duh. I'm sure you're picking up the pattern. Your ult is very important. Some people say "Q, duh, it does damage" Of course it does, but it may not always be a good choice when Ulting to close distance faster is a better idea / choice.
Understand that KZ is feast or Famine. When you hover or even consider him, keep that in mind (as with most assassins).
are super solid options on him when it comes to AD. As with KZ ult, build accordingly. Account for burst, who's fed, and what you can do to improve situations.
: "Sharpening my claws..."