+apply (le_rewl ??? (0+x) (zero_neutral ??));
+apply (le_rewl ??? (x+0) (plus_comm ???));
+apply (le_rewl ??? (x+(-z+z))); [apply feq_plusl;apply opp_inverse;]
+apply (le_rewl ??? (x+(z+ -z))); [apply feq_plusl;apply plus_comm;]
+apply (le_rewl ??? (x+z+ -z)); [apply eq_symmetric; apply plus_assoc;]
+apply (le_rewr ??? (0+y) (zero_neutral ??));
+apply (le_rewr ??? (y+0) (plus_comm ???));
+apply (le_rewr ??? (y+(-z+z))); [apply feq_plusl;apply opp_inverse;]
+apply (le_rewr ??? (y+(z+ -z))); [apply feq_plusl;apply plus_comm;]
+apply (le_rewr ??? (y+z+ -z)); [apply eq_symmetric; apply plus_assoc;]
+apply (og_ordered_abelian_group_properties ??? (-z));
+assumption;
+qed.