∀ {R : Type u} {M : Type v} [inst : Monoid R] [inst_1 : AddMonoid M] [inst_2 : DistribMulAction R M]
  [inst_3 : DistribMulAction Rᵐᵒᵖ M] (x : TrivSqZeroExt R M) (r : R), x * TrivSqZeroExt.inl r = MulOpposite.op r • x