  Magnetic properties of the antiferromagnet Zn$_{0.15}$Cu$_{1.85}$V$_2$O$_7$
(ZnCVO) have been thoroughly investigated on powder and single-crystal samples.
The crystal structure determination using powder x-ray and neutron diffraction
confirms that ZnCVO with Zn = 0.15 is isostructural with
$\beta$-Cu$_{2}$V$_2$O$_7$ ($\beta$-CVO) with small deviation in the lattice
parameters. Macroscopic magnetic properties measurements also confirm the
similarity between the two compounds. The Cu$^{2+}$ spins were found to align
along the crystallographic $c$-axis, antiparallel to their nearest neighbors
connected by the leading exchange interaction $J_1$. Spin dynamics reveals a
typical symmetric spin-wave dispersion with strong interactions in the
$bc$-plane and weak interplane coupling. The exchange interaction analysis
indicates that the spin network of ZnCVO is topologically consistent with the
previous DFT prediction but the values of leading exchange interactions are
contradictory. Furthermore, rather than the predicted 2D honeycomb structure,
the spin network in ZnCVO could be better described by the anisotropic 2D spin
network composing of $J_1$, $J_5$, and $J_6$ interactions, four bonds per one
spin site, coupled by weak interplane interactions.
