  We study the zero-range process on a simple diamond lattice with open
boundary conditions and determine the conditions for the existence of loops in
the mean current. We also perform a large deviation analysis for fluctuations
of partial and total currents and check the validity of the Gallavotti-Cohen
fluctuation relation for these quantities. In this context, we show that the
fluctuation relation is not satisfied for partial currents between sites even
if it is satisfied for the total current flowing between the boundaries.
Finally, we extend our methods to study a chain of coupled diamonds and
demonstrate co-existence of mean current regimes.
