-- Lean 4 proof step from Mathlib.LinearAlgebra.CliffordAlgebra.Contraction (goal)
Goal:
R : Type u1
inst : CommRing R
M : Type u2
inst_1 : AddCommGroup M
inst_2 : Module R M
Q : QuadraticForm R M
d : Module.Dual R M
x : CliffordAlgebra Q
m : M
hx :
  Eq (α := CliffordAlgebra Q)
    ((((contractLeft : (a : Module.Dual R M) → CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) d :
            CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) :
          (a : CliffordAlgebra Q) → CliffordAlgebra Q)
        ((((contractLeft : (a : Module.Dual R M) → CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) d :
              CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) :
            (a : CliffordAlgebra Q) → CliffordAlgebra Q)
          x) :
      CliffordAlgebra Q)
    (0 : CliffordAlgebra Q)
ι_mul :
  Eq (α := CliffordAlgebra Q)
    ((((contractLeft : (a : Module.Dual R M) → CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) d :
            CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) :
          (a : CliffordAlgebra Q) → CliffordAlgebra Q)
        (HSMul.hSMul (α := R) ((d : (a : M) → R) m : R) x -
          HMul.hMul (α := CliffordAlgebra Q) (β := CliffordAlgebra Q)
            ((ι Q : (a : M) → CliffordAlgebra Q) m : CliffordAlgebra Q)
            ((((contractLeft : (a : Module.Dual R M) → CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) d :
                    CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) :
                  (a : CliffordAlgebra Q) → CliffordAlgebra Q)
                x :
              CliffordAlgebra Q)) :
      CliffordAlgebra Q)
    (0 : CliffordAlgebra Q)
ι_mul₁ :
  HSub.hSub (α := CliffordAlgebra Q) (β := CliffordAlgebra Q)
      ((((contractLeft : (a : Module.Dual R M) → CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) d :
              CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) :
            (a : CliffordAlgebra Q) → CliffordAlgebra Q)
          (HSMul.hSMul (α := R) ((d : (a : M) → R) m : R) x) :
        CliffordAlgebra Q)
      ((((contractLeft : (a : Module.Dual R M) → CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) d :
              CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) :
            (a : CliffordAlgebra Q) → CliffordAlgebra Q)
          (HMul.hMul (α := CliffordAlgebra Q) (β := CliffordAlgebra Q)
            ((ι Q : (a : M) → CliffordAlgebra Q) m : CliffordAlgebra Q)
            ((((contractLeft : (a : Module.Dual R M) → CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) d :
                    CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) :
                  (a : CliffordAlgebra Q) → CliffordAlgebra Q)
                x :
              CliffordAlgebra Q)) :
        CliffordAlgebra Q) =
    0
⊢ Eq (α := CliffordAlgebra Q)
    ((((contractLeft : (a : Module.Dual R M) → CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) d :
            CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) :
          (a : CliffordAlgebra Q) → CliffordAlgebra Q)
        ((((contractLeft : (a : Module.Dual R M) → CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) d :
              CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) :
            (a : CliffordAlgebra Q) → CliffordAlgebra Q)
          (HMul.hMul (α := CliffordAlgebra Q) ((ι Q : (a : M) → CliffordAlgebra Q) m : CliffordAlgebra Q) x)) :
      CliffordAlgebra Q)
    (0 : CliffordAlgebra Q)
have ι_mul₂ : HSub.hSub (α := CliffordAlgebra Q)
    ((((contractLeft : (a : Module.Dual R M) → CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) d :
            CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) :
          (a : CliffordAlgebra Q) → CliffordAlgebra Q)
        (HSMul.hSMul (α := R) ((d : (a : M) → R) m : R) x) :
      CliffordAlgebra Q)
    (HSMul.hSMul (α := R) (β := CliffordAlgebra Q) ((d : (a : M) → R) m : R)
        ((((contractLeft : (a : Module.Dual R M) → CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) d :
                CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) :
              (a : CliffordAlgebra Q) → CliffordAlgebra Q)
            x :
          CliffordAlgebra Q) -
      HMul.hMul (α := CliffordAlgebra Q) (β := CliffordAlgebra Q)
        ((ι Q : (a : M) → CliffordAlgebra Q) m : CliffordAlgebra Q)
        ((((contractLeft : (a : Module.Dual R M) → CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) d :
                CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) :
              (a : CliffordAlgebra Q) → CliffordAlgebra Q)
            ((((contractLeft : (a : Module.Dual R M) → CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) d :
                  CliffordAlgebra Q →ₗ[R] CliffordAlgebra Q) :
                (a : CliffordAlgebra Q) → CliffordAlgebra Q)
              x) :
          CliffordAlgebra Q)) =
  0
Tactic: rw [contractLeft_ι_mul, map_sub, contractLeft_ι_mul, hx, map_smul, mul_zero, sub_zero, sub_self]