  Our powder inelastic neutron scattering data indicate that \zvo is a system
of spin chains that are three dimensionally tangled in the cubic phase above 50
K due to randomly occupied $t_{2g}$ orbitals of V$^{3+}$ ($3d^2$) ions. Below
50 K in the tetragonal phase, the chains become straight due to
antiferro-orbital ordering. This is evidenced by the characteristic wave vector
dependence of the magnetic structure factor that changes from symmetric to
asymmetric at the cubic-to-tetragonal transition.
