  We present a measurement of the effective weak mixing angle parameter
$\sin^2\theta_\text{eff}^{\ell}$, in $p\bar{p}\rightarrow Z/\gamma^*
\rightarrow \mu^+\mu^-$ events at a center of mass energy of 1.96 TeV,
collected by the D0 detector at the Fermilab Tevatron Collider and
corresponding to 8.6 fb$^{-1}$ of integrated luminosity. The measured value of
$\sin^2\theta_\text{eff}^{\ell}[\mu\mu]=0.23016 \pm 0.00064$ is further
combined with the result from the D0 measurement in $p\bar{p}\rightarrow
Z/\gamma^{*}\rightarrow e^{+} e^{-}$ events, resulting in
$\sin^2\theta_\text{eff}^{\ell} [\text{comb.}]=0.23095 \pm 0.00040$. This
combined result is the most precise measurement from a single experiment at a
hadron collider and is the most precise determination using the coupling of the
$Z/\gamma^*$ to light quarks.
