Convergence versus integrability in normal form, III

In two previous papers we showed that any analytically integrable vector field admits a local analytic Poincaré-Birkhoff normalization in the neighborhood of a singular point. The aim of this paper is to extend this normalization result to the case when the vector field is only integrable in the sense of Darboux: the first integrals are of Darboux type and not necessarily analytic, and the commuting vector fields are meromorphic.