Zombies are undead creatures raised by a necromancer, specialist spell casters, many of whom worship Iorana. The goddess of magic doesn’t judge magic as good or bad. It’s what people do with it.
To be sure, there are good, law-abiding necromancers, but that’s not the image that comes to mind when one is mentioned in polite company, thus many necromancers choose to keep their specialization secret.
But zombies aren’t being tortured or denied their eternal rest. This is a widely held belief that has no merit. Zombies are simply animated corpses. A zombie can’t be made from a person until their soul had already departed for whatever comes next. Se Karn, the god of death isn’t bothered by zombies and neither is Iorana. Unfortunately, in the absence of actual instruction, people tend to invent their own rules, having nothing to do with good and evil.