  This article presents results for the last unknown two-loop contributions to
the $Z$-boson partial widths and $Z$-peak cross-section. These are the
so-called bosonic electroweak two-loop corrections, where "bosonic" refers to
diagrams without closed fermion loops. Together with the corresponding results
for the $Z$-pole asymmetries $A_l, A_b$, which have been presented earlier,
this completes the theoretical description of $Z$-boson precision observables
at full two-loop precision within the Standard Model. The calculation has been
achieved through a combination of different methods: (a) numerical integration
of Mellin-Barnes representations with contour rotations and contour shifts to
improve convergence; (b) sector decomposition with numerical integration over
Feynman parameters; (c) dispersion relations for sub-loop insertions. Numerical
results are presented in the form of simple parameterization formulae for the
total width, $\Gamma_{\rm Z}$, partial decay widths
$\Gamma_{e,\mu},\Gamma_{\tau},\Gamma_{\nu},\Gamma_{u},\Gamma_{c},\Gamma_{d,s},\Gamma_{b}$,
branching ratios $R_l,R_c,R_b$ and the hadronic peak cross-section,
$\sigma_{\rm had}^0$. Theoretical intrinsic uncertainties from missing higher
orders are also discussed.
