  The eigenfunctions and eigenvalues of the master-equation for zero range
process on a ring are found exactly via the Bethe ansatz. The rates of particle
exit from a site providing the Bethe ansatz applicability are shown to be
expressed in terms of single parameter. Continuous variation of this parameter
leads to the transition of driving diffusive system from positive to negative
driving through purely diffusive point. The relation of the model with other
Bethe ansatz solvable models is discussed.
