Energy band theory is the first choice, which is necessary for Si, Ge, GaAs and so on. These elements have medium and close electronegativity; their energy bands are wide in condensed state; so there are many probability to form materials of different property. Chemical bond theory is not enough to describe it, but the basic chemistry rules will not be broken. You can imagine Ga and As can occupy each other's position in GaAs, but this is definitely forbidden in ZnO. Electrons of Zn2+ 3d and O2- 2p are not quite delocalized either.