  Two series of models and their yields are presented in this paper. The first
series consists of 20 Mo models with varying initial metallicity (solar down to
$Z=10^{-8}$) and rotation (Vini=0-600 km/s). The second one consists of models
with an initial metallicity of $Z=10^{-8}$, masses between 20 and 85 Mo and
average rotation velocities at these metallicities (Vini=600-800 km/s). The
most interesting models are the models with $Z=10^{-8}$ ([Fe/H]=~-6.6). In the
course of helium burning, carbon and oxygen are mixed into the hydrogen burning
shell. This boosts the importance of the shell and causes a reduction of the
size of the CO core. Later in the evolution, the hydrogen shell deepens and
produces large amount of primary nitrogen. For the most massive models (M>~60
Mo), significant mass loss occurs during the red supergiant stage. This mass
loss is due to the surface enrichment in CNO elements via rotational and
convective mixing.
  The yields of the fast rotating 20 Mo models can best reproduce (within our
study) the observed abundances at the surface of extremely metal poor (EMP)
stars. The wind of the massive models can reproduce the CNO abundances of the
carbon--rich UMPs, in particular for the most metal poor star known to date,
HE1327-2326.
