Zukii's a pretty solid Ezreal. The champion is a very strong early-mid game champion that slows down end-game. It's not so much that the champion is overpowered, but the combination of Sheen and 35 armor pen(with runes/masteries) makes Mystic shot do a TON of damage from 5 onward. It's also quite potent before sheen since you essentially have 0 mitigation to it unless you buy some early armor. You'd be surprised how much a 700g investment in a chain vest can completely cripple ezreal's ability to take 1/4th of your hp in one mystic shot.
Also, you need to make sure people don't feed him. He's a very easy champion to snowball with if you can land his skill shots. It's very rare that I see an ezreal do anything other than mediocre if he's not completely rolling the game. It's either 10-1-x or 1-4-x. If he doesn't get those early games he quickly falls behind the stronger carries such as jax, yi, tryndamere, tristana, katarina, etc etc.