Using the final deep-inelastic $e^+p$ and $e^-p$ neutral and charged current scattering cross sections from the H1 experiment at the HERA collider the vector and axial-vector couplings $v_q$ and $a_q$ of light quarks $u$ and $d$ to the $Z^0$-boson are determined~\cite{THISPRELIM}.
The uncertainties on the parton distributions functions (PDFs) are accounted for by simultaneously fitting the electroweak parameters and the parameters of the PDFs.
By using data with polarised electron beams in the fit, the precision is improved compared to an earlier analysis.
The combined QCD and electroweak analysis is employed for a consistency study of the Standard Model of Particle Physics in the domain of space-like momentum transfer by determining the masses of the $Z^0$ and $W$-bosons, and by determining the Fermi coupling constant \GF\ or the weak mixing angle \sw\ together with the $W$-boson mass.
The weak mixing angle, defined in the on-shell scheme, is determined simultaneously at various scales in the range of the data of $12<\Qsq<50\,000\GeVsq$ and thus probes the weak interaction at various scales from one process.
All results are found to be compatible with the Standard Model expectations or with the currently most precise values from other data.