Those who are Christ’s have crucified the flesh: This speaks of something that the believer does, being directed and empowered by the Spirit of God.
It was not and is not the sovereign, “unilateral” work of God.
The old man, the self-inherited from Adam, is crucified with Jesus as the sovereign work of God when we are born again.
Romans 6:6 says, Knowing this, that our old man was crucified with Him.
We are simply told to reckon, or account, the old man as dead (Romans 6:11), we are not told to put him to death.
But the flesh is another matter. We are called to choose to work with God to do to the flesh exactly what God did all by Himself to the old man: crucify the flesh.