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HD 93206 is early-type massive stellar system, composed of componentsresolved by direct imaging (Ab, Ad, B, C, D) as well as a compact sub-system(Aa1, Aa2, Ac1, Ac2). Its geometry was already determined on the basis ofextensive photometric, spectroscopic and interferometric observations. However,the fundamental absolute parameters are still not known precisely enough. Weuse an advanced N-body model to account for all mutual gravitationalperturbations among the four close components, and all observational datatypes, including: astrometry, radial velocities, eclipse timing variations,squared visibilities, closure phases, triple products, normalized spectra, andspectral-energy distribution (SED). The respective model has 38 freeparameters, namely three sets of orbital elements, component masses, and theirbasic radiative properties ($T$, $\log g$, $v_{\rm rot}$). We revised thefundamental parameters of QZ Car as follows. For a model with the nominalextinction coefficient $R_V \equiv A_V/E(B-V) = 3.1$, the best-fit masses are$m_1 = 26.1\,M_{\rm S}$, $m_2 = 32.3\,M_{\rm S}$, $m_3 = 70.3\,M_{\rm S}$, $m_4= 8.8\,M_{\rm S}$, with uncertainties of the order of $2\,M_{\rm S}$, and thesystem distance $d = (2800\pm 100)\,{\rm pc}$. In an alternative model, wherewe increased the weights of RV and TTV observations and relaxed the SEDconstraints, because extinction can be anomalous with $R_V \sim 3.4$, thedistance is smaller, $d = (2450\pm 100)\,{\rm pc}$. This would correspond tothat of Collinder 228 cluster. Independently, this is confirmed by dereddeningof the SED, which is only then consistent with the early-type classification(O9.7Ib for Aa1, O8III for Ac1). Future modelling should also account for anaccretion disk around Ac2 component.

Towards a consistent model of the hot quadruple system HD 93206 = QZ Carin\ae: II. N-body model