  We examine the evolution of peculiar velocities of cold dark matter (CDM) in
localized arrays of inhomogeneous cosmic structures in a $\Lambda$CDM
background that can be identified as a frame comoving with the Cosmic Microwave
(CMB). These arrays are constructed by smoothly matching to this cosmological
background regions of Szekeres-II models whose source is an imperfect fluid
reinterpreted as non-comoving dust, keeping only first order terms in $v/c$.
Considering a single Szekeres-II region matched along two comoving interfaces
to a $\Lambda$CDM background, the magnitudes of peculiar velocities within this
region are compatible with values reported in the literature, while the present
day Hubble expansion scalar differs from that of the $\Lambda$CDM background
value by a 10\% factor, a result that might provide useful information to the
ongoing debate on the $H_0$ tension. While the models cannot describe the
virialization process, we show through a representative example that structures
of galactic cluster mass reach the onset of this process at redshifts around
$z\sim 3$.
