  Multiline techniques assuming similar line profiles have become a standard
tool in stellar astronomy for increasing the signal-to-noise ratio (SNR) of
spectropolarimetric measurements. However, due to the widely-used weak field
approximation their benefits could not so far be used for solar observations,
where a large variety of Stokes profiles emerge from local magnetic fields and
measuring weak fields in the quiet Sun remains a challenge. The method
presented here permits us to analyze many lines with arbitrary Zeeman splitting
and to simultaneously deploy Stokes IQUV spectra to determine a common line
profile with the SNR increased by orders of magnitude. The latter provides a
valuable constraint for determining separately field strengths for each
contributing absorber. This method represents an extension of our recently
developed technique of Nonlinear Deconvolution with Deblending (NDD, Sennhauser
et al. 2009), which accounts for the nonlinearity in blended profiles. Equipped
with all those abilities, ZCD is the perfect tool to further increase the
informative value of high-precision polarimetric observations.
