  We report three-dimensional hydrodynamical simulations of shocks (${\cal
M_{\rm shock}}\geq 4$) interacting with fractal multicloud layers. The
evolution of shock-multicloud systems consists of four stages: a
shock-splitting phase in which reflected and refracted shocks are generated, a
compression phase in which the forward shock compresses cloud material, an
expansion phase triggered by internal heating and shock re-acceleration, and a
mixing phase in which shear instabilities generate turbulence. We compare
multicloud layers with narrow ($\sigma_{\rho}=1.9\bar{\rho}$) and wide
($\sigma_{\rho}=5.9\bar{\rho}$) log-normal density distributions characteristic
of Mach $\approx 5$ supersonic turbulence driven by solenoidal and compressive
modes. Our simulations show that outflowing cloud material contains imprints of
the density structure of their native environments. The dynamics and disruption
of multicloud systems depend on the porosity and the number of cloudlets in the
layers. `Solenoidal' layers mix less, generate less turbulence, accelerate
faster, and form a more coherent mixed-gas shell than the more porous
`compressive' layers. Similarly, multicloud systems with more cloudlets quench
mixing via a shielding effect and enhance momentum transfer. Mass loading of
diffuse mixed gas is efficient in all models, but direct dense gas entrainment
is highly inefficient. Dense gas only survives in compressive clouds, but has
low speeds. If normalised with respect to the shock-passage time, the evolution
shows invariance for shock Mach numbers $\geq10$ and different cloud-generating
seeds, and slightly weaker scaling for lower Mach numbers and thinner cloud
layers. Multicloud systems also have better convergence properties than
single-cloud systems, with a resolution of $8$ cells per cloud radius being
sufficient to capture their overall dynamics.
