Oh my god use your brain! How many times has kean misscontrolled the ball and it's lead to a goal? Not that many.
How many times has zouma let his man go because he's day dreaming and it's cost us a goal?
Keans was a mistake anyone can make those. Zoumas is a constant in his lack of defensive intelligence and that's the point it's not wheather this instance was the one that cost us a goal it that this part of his game costs us goals In general.
Look at the goal against city he gets so caught up ball watching he totally looses his man and doesn't even end up jumping for the ball.
You're sort of arguing against your own point here, in your desperation to somehow salvage some semblance of coherence after you completely ballsed up the original point.
If Keane never miscontrols the ball then there's no need for Zouma to assume he will on this occasion, and he's therefore quite within his rights to let Vardy go and hold his own position like a good centre half should. Zouma letting Vardy go only becomes an issue if we believe that Keane can't usually be trusted to stop a ball travelling at around 1mph from going past him and so Zouma should always be alert to the possibility of him cocking up. Unfortunately you've inadvertently stumbled on a valid line of argument there.
Keane's dreadful, he hasn't improved one iota this year, we've just hidden it better. Zouma has lots of faults but is at least not lacking most of the attributes I would look for in a centre half, and Mina has looked pretty ropey from what I've seen so far, but can be given plenty of slack bearing in mind the injuries and acclimatisation he's been dealing with.