Rav Yaakov Emden infamously wrote a scathing polemic against the Zohar called Mitpachas Soferim. My impression is his conclusion is that it is neither ancient nor authoritative, and is a forgery by Rav Moshe de Leon.
Yet, from what I've seen and heard, he heavily refers to and quotes from the Zohar in his siddur Beis Yaakov. This surprises me, as why would he reference something he felt was a forgery? How can this inconsistency be reconciled?
(Perhaps my premises are wrong, which would be a good answer. However, I don't want answers that understand like the Chida in Shem HaGedolim, who suggests that Rav Yaakov Emden didn't really mean what he wrote in Mitpachas Seforim).