Just double checking this, because it doesn't seem entirely clear. If a non-epic, non-legendary living creature gets reanimated from the effect of rise again, can that creature also become an eternal servant? Rise again says that the creature becomes a zombie when it "comes into play", and the eternal servant effect also says "comes into play". So are these simultaneous, like a nullify and reverse magic on the same target at the same time (you can only choose one and afterwards the other can't take effect), or simultaneous like burn damage and regeneration (both take effect, but their controller chooses the order).
Thematically, it feels like the eternal servant ability should work on any non-epic, non-legendary undead creature, regardless of whether they used to be alive or not, because presumably ALL undead creatures USED TO BE ALIVE.
It doesn't make sense to me thematically that I could not make a creature my eternal servant if it becomes a zombie when it comes into play, but I would still like to be more clear on this from a rules perspective.