Zero-Tails Void was said to be a tailed beast, but it actually had little connection to the Nine Tailed Beasts.
Its only connection was likely that it required the immense Chakra of a tailed beast to be created.
Furthermore, the conditions for the birth of Zero-Tails Void were extremely harsh.
Besides requiring tailed beast Chakra as the final catalyst, its creation also required an enormous amount of Dark Chakra.
Dark Chakra did not naturally exist in the Ninja World and had to be artificially created.
It required drawing upon the darkness within a person's heart to produce Dark Chakra.
At present, only the Sky Ninja possessed this technique.
Over the years, Shinnō had operated throughout the Ninja World as a medical ninja while searching for suitable pawns, drawing out the darkness in their hearts and extracting Dark Chakra from them!
After gathering enough Dark Chakra, Shinnō had been waiting for an opportunity.
An opportunity to capture a tailed beast.
Originally, Shinnō had set his sights on Konoha's Nine-Tails Jinchuriki.
That was when, in the eyes of outsiders, Kushina Uzumaki and Minato had just died. Shinnō believed that the new Nine-Tails Jinchuriki would be the most suitable target.
However, for some unknown reason, just when everyone in the Ninja World, including Shinnō, believed Konoha would decline because of the Fourth Hokage couple's deaths—
Konoha suddenly produced one Kage-level powerhouse after another!
Moreover, there were even more powerful Elite Jonin!
Konoha's unreasonable strength made Shinnō abandon his original resolve to capture the Nine-Tails Jinchuriki.
The reason Shinnō had initially targeted the Nine-Tails was because it was the strongest of the Nine Tailed Beasts.
Zero-Tails Void created with the Nine-Tails' Chakra would also have been even stronger.
But there was no helping it. Konoha had too many powerhouses, and he no longer dared