Any statement about the tenth Aethyr belongs to one of three layers of the record, and they are roughly three centuries apart. Saying which layer a claim comes from is most of what can honestly be said about an individual Aethyr.
The tenth Aethyr and the working at Bou Saada
ZAX is the Aethyr around which the best known and most discussed Enochian working turns. Crowley and Victor Neuburg conducted it in the Algerian desert near Bou Saada in December 1909, and Crowley's account of what was encountered there, under the name Choronzon, is the passage of The Vision and the Voice most often quoted and most often reproduced without its date.
That account is Crowley's, from 1909. Choronzon appears in the earlier Dee and Kelley material as a name; the character, the role and the whole narrative attached to it in modern usage belong to Crowley's record and to the writers who followed him.
The diaries, 1580s
The name ZAX, its place as the tenth of the thirty, and the governors assigned to it all come from the scrying sessions of John Dee and Edward Kelley in the 1580s. In that material the thirty Aethyrs divide the earth between ninety-one governors: twenty-nine Aethyrs hold three each and the thirtieth holds four. This atlas carries all ninety-one, and the arithmetic can be checked against them.
Why the layers are kept apart here
The three are separated in this atlas because they make different kinds of claim. The diaries supply the names and the structure, the order supplies a ritual context, and Crowley supplies the descriptions. Attributing any of the three to another is the commonest error made about this material.