Healer Unit 0 already had masters so why was she so accepting of Zodan when he arrived and claimed her as his own? That was because of what happened to her previous owners the ones whose actions were the reason that she was roboticized in the first place after all. It was through their own greed and desire to control something that was beyond their understanding regardless of the reasoning for their doing so. They claimed that they were doing this was the betterment of White Magic as a whole. However, they did not understand what that type of magic truly was in the first place as they only knew about the healing and support side of it. Thus that is where all their focus and attention was on as they never knew its true nature and origins after all. However, they could not possibly know that because they were just mortals after all as there was no way they could have possibly figured it out without getting to and/or close to godhood themselves.
They had merely found a loophole and were exploiting it for their own gain in the end. As their intention might have been good their execution of those intentions was the problem and thus they were now facing the results of their own action. Though the roboticization of Ancu herself as she was merely the Goddess of Healing overlooked the very concept of White Magic itself. Since leaders of the Healer's Association had gone about roboticization the very source of their magic itself. They had unknowingly and unintentionally tainted it beyond recovering. There was no way to restore Ancu and not healing magic to its original untainted form anymore. Though the taint that was now with White Magic itself was luckily contained to merely the type that healers used themselves. This taint was not necessarily anything bad and/or evil to start with as something getting tainted does not always mean evil after. Taint itself in this instance only means contaminate or pollute as there is no good or evil/light or darkness/positive or negative spins to this.
It is just a result of Ancu herself being roboticized into an automaton herself. That metallic, inorganic, and strictly logical aspect was now present within all that desired the usage of what was viewed as traditional White Magic by the mortals. As is they were able to use their connection to trigger Ancu's roboticization then the reverse would be possible as well but on a large scale that only saving graces were twofold at the moment:
1. It only affected healing and healing adjacent magic (typical status support of healer)
2. Even though they were constantly being exposed it the same process it was a diluted version of what roboticized Ancu.
Since it was a diluted version this was how mortals thought their magic was getting better as they were accessing it and unknowingly using it like a machine would. The magic itself was now doing all the hard work they just needed to channel it through themselves and guide it along their desired path. However, this is where the danger comes in as even something diluted will eventually cause a problem and/or just result in their full roboticization if they do it long enough. That or they use way more tainted healing and 'traditional' White Magic than their bodies can handle. Once they cross over that line then its be the beginning of the end of their life as mortals and on the straight path they become automatons themselves.
However the amount and/or level of healing White Magic was unknown at the moment it was merely enough to overwhelm the body either at once and/or over time to cause them to become an automaton. That was now the fate of all those who use Ancu's type of magic from now on with the focus on healing and healing adjacent magics causing it to happen.
So this was now the fate of those that were exposed to her magic for the allowed amount of time or the long term dosage of it. Then what of those who were the ones behind her roboticization in the first place? They were the ones who should be exposed to the most potent and direct forms of her magic being the ones that were giving her orders directly through the metallic replica that was used as not just her one way mirror into the mortal world. It was now her two way connection to it that allowed her to not only see into the mortal world but directly communicate with any and everyone through it.
The fates of her original owners were ones that would possibly be the most unique of all those that would come after them and quite possibly on par with the second most unique of them all. The first place is the roboticization of Ancu herself into Healer Unit 0. The leaders of the Healer's Association were exposed to so much of her magic and it was so potent the amount they were exposed to that they did not just become roboticized into automaton versions of themselves like all others even Ancu herself would as a result of it.
Oh on....their fates were far different as they did not listen to the stories about flying too close to the sun and the dangers of doing so. Anything that can be given can be altered and then taken away in the exact same manner yet opposite manner compared to when they were in the giving phase. Those leaders ignore this warning because of mortal hubris and misunderstanding of how the world works in reality rather than how they assumed it worked with their limited capacity to do so.
The leaders of the Healer's Association did become roboticized into automaton however they were not one of themselves but instead, they were replicas of Ancu herself. Not the type where there were now automaton versions of herself with a copy of her entire self overwriting their original selves. No, they were merely replicas of the metallic replica that they built that would unknown to them give them control over Ancu. They were exposed to magic so vast and so potent that it literally wiped their very existence out itself leaving behind nothing to prove their ever existence as anything other than basically serval more terminal that would allow Healer Unit 0 to communicate and receive communication from the mortal world going forward. Thus why Zodan was able to claim Healer Unit 0 as his own as she no longer had owners to give her orders and direct her anymore. Her previous ones ceased to exist anymore thus the only thing she had until he arrived was not owners just more terimnal to convey and have things conveyed to her to and from the mortal world.