"New York does not recognize civil conspiracy to commit a tort as an independent cause of action; rather, such a claim stands or falls with the underlying tort (see Hebrew Inst. for Deaf & Exceptional Children v Kahana, 57 AD3d 734, 735; Salvatore v Kumar, 45 AD3d 560, 563)."
Sounds more like a fraudulent concealment, conversion or both. The issue would be proving intent and connecting. How would the accountant know if the so called embezzler was providing false information for the returns? Who hired the accountant?
You need to seek a consultation with a qualified attorney ASAP because there may also be statute of limitations issues. A detailed and fact sensitive consultation is also required for an attorney to address your question.