Note the Sadducees didn't believe in life after death. Hence they were sad, you see?
They were among Jesus' opponents. We're concerned with what his opponents believed. If they believed they could send Jesus to hell or annihilate his soul, then it makes sense to me since the Qur'an is denying a claim
made by them and not the historical event itself. Even if one doesn't believe in annihilation, hell can be viewed as a form of death for the soul.
This puts the horse before the cart. The horse is they couldn't kill Christ's soul. The cart as per my argument is they can't destroy any soul. Not that any human can even conceivably destroy any soul. The cart is that no soul will be destroyed by God - period. Because doing so is a contradiction in terms, it is incoherent. It is defined out of possibility.
"And do not invoke with Allah another deity. There is no deity except Him. Everything will be destroyed except His Face. His is the judgement, and to Him you will be returned" (Qur'an 28.88).
One can understand hell as a form of destruction and death.
Everything is passing away except the face of Allah (infinity - the face of Allah = all infinity, the human soul = a portion of that substance).
The Face of Allah is infinity. I am tempted to say it is the same as the soul of Allah. Or maybe the Face is the outer expression, whereas the soul is the inner. Either way, it is infinity.
The human soul is of infinity. That's why it's a-okay for our creator to send us to hell for eternity for doing wrong (or even for doing right) - because he is all there is, really.
The human soul is not passing away as it is of the same thing as the Face of Allah. In fact the verse you cite kind of supports this, by saying, everything is passing away ... yet we will return to Allah. What remains to return to Allah? The soul, which always was from the Nur (Light) of Allah. So l hope you see how it is redundant to put cute codes that "Christ = soul, and they couldn't destroy Christ's soul but by implication they did kill him bodily!" when in fact no souls are destroyed and we're bypassing the obvious blaring prima facie message that they couldn't kill Christ at the time they sought to kill his body by nailing him to a cross (that is a very corporal punishment, buddy). That's the prima facie message. Sorry @ the sectarians!
All knowledge is the Face of Allah too, that's why the spiritual seeker and the scientist are in many ways the same.
So l hope l have given you an idea of the soul being infinite and undying, and how this is not contradicted by the Qur'an, and so the special case for Christ being code for the soul of Jesus hence we have a coded message that they couldn't destroy Christ's soul, is baseless and obviated by the fact that we can't destroy souls anyhow, not just Christs's, but anybody's.
As for Hell: the soul does not die in hell. Even in this life, the soul never dies. The body dies in this life, and in hell, the body dies perpetually, being killed over and over e.g. by having skin burnt off and replenished.
Note that where l am in doubt, l am happy to speculate. But l don't crystallise into intractable viewpoints like the various sects have done. We have a tradition that "difference of opinion is a blessing on this community" (paraphrased). Look how the sects have crystallised on this baseless viewpoint which originally was just speculation but l have now shown how it's not even speculative it's demonstrably false / redundant. Although l'll admit l haven't shown my working out re: how the essence of Allah = pure existence, but l do have a logical derivation for it.
We are encouraged to debate, even obscure things like this. But the sects create intractable viewpoints whereas the viewpoints on obscure topics were always just stimuli for spiritual growth through endless enquiry.