The light quark masses mu,d,s are fundamental parameters of Quantum ChromoDynamics (QCD) and ought to be constrained as accurately as possible. Of particular interest is the mass difference between the up and down quarks, md-mu, that measures isospin breaking in strong interactions. We will investigate the three-pion system in h¢®ppp decays and the access offered by these transitions to md-mu. The question is whether independent information on the latter can directly be inferred from the decay dynamics, like the unique way offered by the partner reaction h®ppp [1]. We will perform a partial wave decomposition of the amplitude combining Chiral Perturbation Theory with dispersion relations and compare it to the very recent, high-precision experimental data released by the BESIII Collaboration [2] to answer this question.