If we think of the familiar narrative voices as concentric circles then we have, in the outer circle, the third-person narrator, who is detached from what they're describing ('he/she did this and that', etc.); then the second-person voice, where the narrator is closer to what they're describing because they address the reader directly (with 'you did this and that', etc.); and then, in the innermost circle, the first person ('I did this and that'), which is the narrator talking about themselves.
So the zero- or zeroth-person narrative would be an infinitely small but infinitely dense point in the centre of the circles, where the text becomes a mutus liber and communicates its contents to the reader without a narrative voice at all.
The Death of the Author is therefore the birth of the silent scribe, the ever-living ghost writer who expresses the true story of the world in this zeroth-person voice.