Which Russia cannot provide since they already promised not to invade.
I'm not sure how much that matters in practice, since nukes can be delivered by submarine or through ICBMs, but regardless, that's what Russia wants and a DMZ won't address that demand.
(Disarmament was one of the Russian asks during yesterday's negotiations. It was rejected ofc.)
The world is connected like never before and there are no unipolar winners or losers any more (if there ever were, considering the squandered individual, society-wide, and world-wide human potential when people die).
At the very least this is likely to lead to a global depression.
That's if we avoid WW3, which would devastate the entire world if it happened.
Such guarantees are worthless.
It's also clear that the rest of NATO is not willing to directly fight against Russia to save Ukraine, so NATO membership for Ukraine is just as worthless.