Pendulum Effect
You can target 1 face-up monster on the field; change its DEF to 0 until the end of this turn (even if this card leaves the field). You can only use this effect of "D/D/D Supersight King Zero Maxwell" once per turn.
Witchcrafter Madame Verre: "Yameteee"
I think you can still increase its ATK again. There's a similar ruling for the Reptilianne archetype:
https://yugioh.fandom.com/wiki/Card_Rulings:Reptilianne_Gorgon#cite_note-ReptGorgon-Shrink-5
"If a monster's ATK is 0 because it battled with "Reptilianne Gorgon" and then it is equipped with an Equip Spell Card, then the monster's ATK is increased from 0"
Reptilianne Gorgon's effect doesn't specify any duration (e.g. until the end of the turn). The ATK of any monster it attacked can still be increased afterwards.
This one and Clausolas says "until the end of this turn"