A new Kirchhoff-type true-amplitude migration to zero-offset (MZO) algorithm is proposed for 2.5-D common-offset reflections in 2-D laterally inhomogeneous layered isotropic earth models. It provides a transformation of a common- offset seismic section to a simulated zero-offset section and is thus closely related to a dip-moveout correction (DMO). The simulated primary zero-offset reflections, even from curved interfaces, have the best possible signal character, i.e., the geometrical-spreading factor of an original primary common-offset reflection is replaced by that of a correct zero-offset reflection. A single weighted stacking procedure needs to be performed only similar to the familiar Kirchhoff or diffraction-stack migration. Moreover, in analogy to true-amplitude Kirchhoff migration, the weight function can be computed by dynamic ray tracing in the macro-velocity model which is supposed to be available. As the simulated zero-offset reflection amplitudes are controlled by the zero-offset geometrical-spreading factor and the (angle-dependent) offset reflection coefficients, one can thus perform a post-MZO, but pre-migration AVO analysis. If compared to correct zero-offset reflections, the simulated ones turn out to be stretched (frequency shifted) by the cosine of the reflection angle.