If we're only considering the level of difficulty, then Kornov would naturally be the choice to go for.
Because Kornov works in the Duma, and the Duma is practically Wang Ye's "private land"!
Grezlov, Rilinov, those are all standing on the same line as Wang Ye. Together, the three of them can definitely secure the majority of the Duma's votes. If you want to do something within the Duma, no one can stop it!
So, targeting Kornov wouldn't be difficult.
However, Wang Ye was considering what was the point of targeting Kornov...
Now, Kornov is just a marginalized Vice Speaker, not holding any significant committee chairmanship roles. You can hardly hear his "voice" within the Duma.
Even if his Vice Speaker position was taken away from him, what would that achieve...
Therefore, Wang Ye found that targeting Kornov was not very meaningful and would not truly harm the Moscow Faction.
That left only Luzhikov as an option!