  We study the gluon fusion into pairs of off-shell Z bosons and their
subsequent decay into charged lepton pairs at hadron colliders. We do not
restrict the intermediate state Z bosons to the narrow width approximation but
allow for arbitrary invariant masses. We compare the strength of this process
with the known leading order results for q q_bar -> Z Z -> 4 l and for g g -> H
-> Z Z -> 4 l .
