  Strong spin-orbit coupling (SOC) effects of heavy $d$-orbital elements have
long been neglected in describing the ground states of their compounds thereby
overlooking a variety of fascinating and yet unexplored magnetic and electronic
states, until recently. The spin-orbit entangled electrons in such compounds
can get stabilized into unusual spin-orbit multiplet $J$-states which warrants
severe investigations. Here we show using detailed magnetic and thermodynamic
studies and theoretical calculations the ground state of Ba$_3$ZnIr$_2$O$_9$, a
6$H$ hexagonal perovskite is a close realisation of the elusive $J$~=~0 state.
However, we find that local Ir moments are spontaneously generated due to the
comparable energy scales of the singlet-triplet splitting driven by SOC and the
superexchange interaction mediated by strong intra-dimer hopping. While the Ir
ions within the structural Ir$_2$O$_9$ dimer prefers to form a spin-orbit
singlet state (SOS) with no resultant moment, substantial interdimer exchange
interactions from a frustrated lattice ensure quantum fluctuations till the
lowest measured temperatures and stabilize a spin-orbital liquid phase.
