From the late thirteenth century a second Shimon bar Yochai exists alongside the first. The Zohar, which begins circulating in Castile in the 1280s, is written largely in an artificial Aramaic and presents itself as the record of a circle gathered around the second-century sage as they walk through the Galilee expounding the Torah. He is its central voice, and the authority the book carries in later Judaism rests on that claim.
Gershom Scholem argued that the Zohar was composed in Castile by Moses de Leon, on the evidence of its language, of that Aramaic's dependence on medieval Hebrew idiom, and of the close correspondences between the Zohar and de Leon's signed Hebrew works. That case has been the scholarly default since 1941. Yehuda Liebes accepted the medieval dating but argued that a circle of writers rather than a single hand stands behind the book, which leaves authorship open in a way Scholem's version does not.
Nothing here is settled by asserting one side. The traditional position holds the sage to be the author and the medieval manuscripts to be transmission. The scholarly position holds the ascription to be pseudepigraphic, a device with long precedent in Jewish literature, where a work is placed in the mouth of an earlier authority to say where it belongs rather than to deceive anyone about who held the pen. The atlas records the attribution as disputed and names both camps, because the disagreement is real and is itself a part of the Zohar's history.