Originally Posted by BG-57
I asked the very same question long ago and I think I've worked out the problem:
The Dragon Zombies in the right path may cast Pandora's Box once, but a bug prevents them from using it again. At least in the original American PSX version.
However, the Dragon Zombies in the center pit will freely use Pandora's Box many times, usually as a final attack.
You can equip more than one E-skill materia on the same character, as long as have growth slots and they carry the same E-skills.