Zaishen Chest drops from unowned campaigns

Is it possible for weapon skins of an unowned campaign to drop, e.g. a Voltaic Spear dropping for one who doesn't own EotN?

yes
all z-chest drops are the same no matter which/how many campaigns you own and/or don't own.

Offtopic: Voltaic Spear drops from UW and FoW chest as well, which can be accessed from every campaign.