  Critical exponents of the infinitely slowly driven Zhang model of
self-organized criticality are computed for $d=2,3$ with particular emphasis
devoted to the various roughening exponents. Besides confirming recent
estimates of some exponents, new quantities are monitored and their critical
exponents computed. Among other results, it is shown that the three dimensional
exponents do not coincide with the Bak, Tang, and Wiesenfeld (abelian) model
and that the dynamical exponent as computed from the correlation length and
from the roughness of the energy profile do not necessarily coincide as it is
usually implicitly assumed. An explanation for this is provided. The
possibility of comparing these results with those obtained from Renormalization
Group arguments is also briefly addressed.
