Zenitsu vs Inosuke.
Both are comparable but I think that we saw better feats from Zenitsu.
( Im a Zenitsu pfp so please dont take that as a sign of being based )
Inosuke has a bigger move set, spatial awarness, can move his organs etc.
There really isnt much evidence supporting which one is stronger beacuse most of the times they were shown as euals or one was fighting with a stronger / weaker opponent.
But there is one chapter where we clearly saw the answer to this question.
Chapter 199.
Inosuke was going all out on Muzan and if you look closely he barely avoided / sliced his attacks.
Than Zenitsu used Thunderclap and Flash on Muzan with no effect ( or just happend of screen )
Than he said - " I dont have enough stamina, one of my legs is broken , this will be my last good attack "
and unleashed Flaming Thunder God which actually injured Muzan quite badly ( he looked furious and as if he was in pain ).
And Zenitsus reaction was - "Too shallow, it has to be a shining red blade or the wound wont be deep enough "
Than he felt on the ground and needed Inosukes help cuz Muzan arleady striked his tentacles.
After that Muzan used the Shockwave attack and Tanjirou protected Inosuk ETC.
Zenitsu stood up and started attacking again and after each attack his lines were like - "I cant get fast enoug ", " Im losing strenght"
Muzan started 1v1 against Tanjirou and when he nearly striked him, Zentisu used Godspeed Thunderclap and flash -
and he actually send Muzan few meters away / pushed him with his pure strenght alone. And right after that he was sliced by Muzan.
Zenitsu with cracked skin on his entire body, blood loss from many attacks, two broken legs did much better against Weakened Muzan than Inosuke.
Of coure Inosuke was also injured but much less and didnt need to be carried unlike Zenitsu ( I mean his power comes from his legs and his injuries are just consequences of him over-using his power but my point stands still ).
So the fight could go in two ways.
1. Zenitsu Speed Blitz.
His speed is comparable to Inosuke when his not using his forms but when he enters God Speed, Inosuke will be overwhelmed and propably one shotted.
2. Inosuke wins by avoiding attacks.
Zenitsus techniqe has a big flaw - it drains him of stamina and after using few Godspeeds his legs break and he gets much weaker / slower.
Zenitsu requires few seconds to launch his attacks so if Inosuke wont allow him to do that then he will lose.
Tbh I think its a fair much, both have enough hacks and diffrent fighting styles so its hard to scale.