  We study the $e^+ e^- \to K^+ ( D_s^{*-} D^0 + D_s^- D^{*0})$ reaction
recently measured at BESIII, from where a new $Z_{cs}$ state has been reported.
We study the interaction of $\bar D_s D^*$ with the coupled channels $J/\psi
K^-$, $K^{*-} \eta_c$, $D_s^- D^{*0}$, $D_s^{*-} D^0$ by means of an extension
to the charm sector of the local hidden gauge approach. We find that the $D_s^-
D^{*0}+ D_s^{*-} D^0$ combination couples to $J/\psi K^-$ and $K^{*-} \eta_c$,
but the $D_s^- D^{*0}- D_s^{*-} D^0$ combination does not. The coupled channels
help to build up strength in the $D_s^- D^{*0}+ D_s^{*-} D^0$ diagonal
scattering matrix close to threshold and, although the interaction is not
strong enough to produce a bound state or resonance, it is sufficient to
produce a large accumulation of strength at the $\bar D_s D^*$ threshold in the
$e^+ e^- \to K^+ ( D_s^{*-} D^0 + D_s^- D^{*0})$ reaction in agreement with
experiment.
