set G = the AddGroup;
set z = ZERO ( the AddGroup, the AddGroup);
fun (ZERO ( the AddGroup, the AddGroup)) is additive ;
then ZERO ( the AddGroup, the AddGroup) is GroupMorphism-like by Def18;
hence ex b₁ being GroupMorphismStr st
( b₁ is strict & b₁ is GroupMorphism-like ) ; :: thesis: verum