Semihypergroups obtained by merging of 0-semigroups with groups

We consider the class of 0-semigroups (H,*) that are obtained by adding a zero element to a group (G,?) so that for all x,y ? G it holds x * y ? 0 => x * y = xy. These semigroups are called 0-extensions of (G,?). We introduce a merging operation that constructs a 0-semihypergroup from a 0-extension of (G,?) by a suitable superposition of the product tables. We characterize a class of 0-simple semihypergroups that are merging of a 0-extension of an elementary Abelian 2-group. Moreover, we prove that in the finite case all such 0-semihypergroups can be obtained from a special construction where (H,*) is nilpotent. nema