It honestly depends on a lot of factors, army composition, that strong general getting any strong subordinates? Gonna use the 3 you provided, along with their combination.
Based on the above stats, this fusion commander would be: 91/92/92
vs
86/92/90
91/86/80
84/88/92
Strategy: I have two dudes are at 90 and 1 on par with that fusion general. Strategically i'm already better. Since I have essentially two people who can rival that 1 general.
Leadership: I got 1 dude who matches the fusion guy while 2 who are still decent at leading. I'm at an advantage leadership wise.
Martially: I got 1 guy who can match the fusion man in combat, and once that happens the fusion man's leadership/strategy become irrelevant due to be isolated in a duel and combat. While the other two can still play a factor and will be better than the general army soldier by a good margin. And they both can influence the Batei vs fusion man fight.
The Fusion commander is gonna lose if he's leading a normal Zhao army vs the other 3 leading a normal Zhao army. Especially when you take into account these three would have "teamwork" as well.
But I would say a general who is 94/94/94 would be able to overcome the trio.
With that said though, could there be scenarios where I prefer that fusion guy over the 3 different ones? Yes 100%. If I have other decent generals already, then I'd much rather have that fusion general, than those 3 separately.