Supernatural Willpower and absorption: Toei's Official timeline
declares Infinite zamasu to be Zamasu's will losing control and engulfing the universe, implies he is not only merging universe 7 and becoming it, but instead engulfing it into his own will which is infinite zamasu
Abstract existence (type 1): Before people make objectionable comments, calm down and hear me say why. This is not because he becomes the concept of "justice and order" that has been rejected before because of flowery language And metaphor (or Gowasu's interpretation of Zamasu's justice). It is because he becomes the law of the universe
Similar to the case of Gods (shinza) , although on a much smaller and incomparable scale. Also IZ is the will of zamasu himself trying to be his own justice,
defined as the universe/world itself, its law, knowledge and power and Kill all mortals which explains why zamasu's will (Infinite zamasu) try to fusion and engulf the universe, that's because it's his self-centered idea of justice. Even this Zeno don't have conceptual or law EE. He destroy Future timeline's universe 7 in anime (maybe timeline) , IZ is universe 7 itself and its law, its law being erased because its universe no longer exist
Or if this being rejected, edit AP's IZ explanation