Evolution at very low and zero Z
  Rotation deeply affects the evolution of very metal poor massive stars. Indeed, even moderately rotating stars reach the break--up limit during the Main--Sequence (MS) phase, they evolve rapidly to the red after the core H--burning phase and important surface enrichment in CNO elements occurs at the supergiant stage. High rotation and the self enrichment in heavy elements $Z$ tend to enhance the quantity of mass lost by stellar winds. As a numerical example, we obtain that a 60 M$_\odot$ at $Z=0.00001$, with an initial rotation corresponding to 0.7 of the critical velocity, loses half of its initial mass during its lifetime. The ejected material, enriched in helium and CNO elements, has interesting consequences for the early chemical evolution of galaxies. 
Georges Meynet, Andr\'e Maeder and Sylvia Ekstr\"om