No, not synonymous. Amazona xanthops, like all amazons, is a parrot of the American clade of parrots (Arinae). Poicephalus, like Poicephalus flavifrons, is African like all the genus, and belongs to Psittacinae.
@Kakapo - The Yellow-faced Amazon has been placed in a monotypic genus, Alipiopsitta (erected in 2006). Whether one agrees with that generic change or not, it has nothing to do with the African Poicephalus.
@Goura , maybe you can put here again your deleted question about the status of this species with respect to Poicephalus flavifrons, so then Dave can calm down?
@TeaLovingDave That's probably my fault, because in my original title (posted in the "Animal or zoo identification" gallery), I asked if these two species were synonymous. After receiving the responses from Kakapo & Chlidonias, I moved it to this gallery and changed the title.
@Goura (Actually it must have been re-titled before I replied, because I never saw the original question and thus didn't know the context of Kakapo's post)