Hard to Kill / To the Death and Undead

[Wondering GM]

I'm basically wondering if Hard to Kill and To the Death override the fact that undead are destroyed once they reach 0 HP.

Something tells me it's not the case, but I wanted to be certain and couldn't find an answer.

EDIT : Obviously, 3 times a non-existent Constitution score would still be 0, but since Undead use Charisma instead of Constitution, I suddenly had doubts.

[KainPen]

Maybe us CHA instead of Con since undead use that for hp. ect.