-- Mathlib/Algebra/Jordan/Basic.lean
theorem aux2 {a b c : A} :
    ⁅L a, L (a * a)⁆ + ⁅L a, L (b * b)⁆ + ⁅L a, L (c * c)⁆ +
    ⁅L a, 2 • L (a * b)⁆ + ⁅L a, 2 • L (c * a)⁆ + ⁅L a, 2 • L (b * c)⁆ +
    (⁅L b, L (a * a)⁆ + ⁅L b, L (b * b)⁆ + ⁅L b, L (c * c)⁆ +
    ⁅L b, 2 • L (a * b)⁆ + ⁅L b, 2 • L (c * a)⁆ + ⁅L b, 2 • L (b * c)⁆) +
    (⁅L c, L (a * a)⁆ + ⁅L c, L (b * b)⁆ + ⁅L c, L (c * c)⁆ +
    ⁅L c, 2 • L (a * b)⁆ + ⁅L c, 2 • L (c * a)⁆ + ⁅L c, 2 • L (b * c)⁆)
    =
    ⁅L a, L (b * b)⁆ + ⁅L b, L (a * a)⁆ + 2 • (⁅L a, L (a * b)⁆ + ⁅L b, L (a * b)⁆) +
    (⁅L a, L (c * c)⁆ + ⁅L c, L (a * a)⁆ + 2 • (⁅L a, L (c * a)⁆ + ⁅L c, L (c * a)⁆)) +
    (⁅L b, L (c * c)⁆ + ⁅L c, L (b * b)⁆ + 2 • (⁅L b, L (b * c)⁆ + ⁅L c, L (b * c)⁆)) +
    (2 • ⁅L a, L (b * c)⁆ + 2 • ⁅L b, L (c * a)⁆ + 2 • ⁅L c, L (a * b)⁆)

Proof state:
A : Type u_1
inst✝¹ : NonUnitalNonAssocCommRing A
inst✝ : IsCommJordan A
a b c : A
⊢ ⁅L a, L (b * b)⁆ + ⁅L a, L (c * c)⁆ + ⁅L a, 2 • L (a * b)⁆ + ⁅L a, 2 • L (c * a)⁆ + ⁅L a, 2 • L (b * c)⁆ +
        (⁅L b, L (a * a)⁆ + ⁅L b, L (c * c)⁆ + ⁅L b, 2 • L (a * b)⁆ + ⁅L b, 2 • L (c * a)⁆ + ⁅L b, 2 • L (b * c)⁆) +
      (⁅L c, L (a * a)⁆ + ⁅L c, L (b * b)⁆ + ⁅L c, 2 • L (a * b)⁆ + ⁅L c, 2 • L (c * a)⁆ + ⁅L c, 2 • L (b * c)⁆) =
    ⁅L a, L (b * b)⁆ + ⁅L b, L (a * a)⁆ + 2 • (⁅L a, L (a * b)⁆ + ⁅L b, L (a * b)⁆) +
          (⁅L a, L (c * c)⁆ + ⁅L c, L (a * a)⁆ + 2 • (⁅L a, L (c * a)⁆ + ⁅L c, L (c * a)⁆)) +
        (⁅L b, L (c * c)⁆ + ⁅L c, L (b * b)⁆ + 2 • (⁅L b, L (b * c)⁆ + ⁅L c, L (b * c)⁆)) +
      (2 • ⁅L a, L (b * c)⁆ + 2 • ⁅L b, L (c * a)⁆ + 2 • ⁅L c, L (a * b)⁆)

Tactic:
simp only [lie_nsmul]

Result:
A : Type u_1
inst✝¹ : NonUnitalNonAssocCommRing A
inst✝ : IsCommJordan A
a b c : A
⊢ ⁅L a, L (b * b)⁆ + ⁅L a, L (c * c)⁆ + 2 • ⁅L a, L (a * b)⁆ + 2 • ⁅L a, L (c * a)⁆ + 2 • ⁅L a, L (b * c)⁆ +
        (⁅L b, L (a * a)⁆ + ⁅L b, L (c * c)⁆ + 2 • ⁅L b, L (a * b)⁆ + 2 • ⁅L b, L (c * a)⁆ + 2 • ⁅L b, L (b * c)⁆) +
      (⁅L c, L (a * a)⁆ + ⁅L c, L (b * b)⁆ + 2 • ⁅L c, L (a * b)⁆ + 2 • ⁅L c, L (c * a)⁆ + 2 • ⁅L c, L (b * c)⁆) =
    ⁅L a, L (b * b)⁆ + ⁅L b, L (a * a)⁆ + 2 • (⁅L a, L (a * b)⁆ + ⁅L b, L (a * b)⁆) +
          (⁅L a, L (c * c)⁆ + ⁅L c, L (a * a)⁆ + 2 • (⁅L a, L (c * a)⁆ + ⁅L c, L (c * a)⁆)) +
        (⁅L b, L (c * c)⁆ + ⁅L c, L (b * b)⁆ + 2 • (⁅L b, L (b * c)⁆ + ⁅L c, L (b * c)⁆)) +
      (2 • ⁅L a, L (b * c)⁆ + 2 • ⁅L b, L (c * a)⁆ + 2 • ⁅L c, L (a * b)⁆)

Proof state:
A : Type u_1
inst✝¹ : NonUnitalNonAssocCommRing A
inst✝ : IsCommJordan A
a b c : A
⊢ ⁅L a, L (b * b)⁆ + ⁅L a, L (c * c)⁆ + 2 • ⁅L a, L (a * b)⁆ + 2 • ⁅L a, L (c * a)⁆ + 2 • ⁅L a, L (b * c)⁆ +
        (⁅L b, L (a * a)⁆ + ⁅L b, L (c * c)⁆ + 2 • ⁅L b, L (a * b)⁆ + 2 • ⁅L b, L (c * a)⁆ + 2 • ⁅L b, L (b * c)⁆) +
      (⁅L c, L (a * a)⁆ + ⁅L c, L (b * b)⁆ + 2 • ⁅L c, L (a * b)⁆ + 2 • ⁅L c, L (c * a)⁆ + 2 • ⁅L c, L (b * c)⁆) =
    ⁅L a, L (b * b)⁆ + ⁅L b, L (a * a)⁆ + 2 • (⁅L a, L (a * b)⁆ + ⁅L b, L (a * b)⁆) +
          (⁅L a, L (c * c)⁆ + ⁅L c, L (a * a)⁆ + 2 • (⁅L a, L (c * a)⁆ + ⁅L c, L (c * a)⁆)) +
        (⁅L b, L (c * c)⁆ + ⁅L c, L (b * b)⁆ + 2 • (⁅L b, L (b * c)⁆ + ⁅L c, L (b * c)⁆)) +
      (2 • ⁅L a, L (b * c)⁆ + 2 • ⁅L b, L (c * a)⁆ + 2 • ⁅L c, L (a * b)⁆)

Tactic:
abel

Result:
no goals

Proof state:
A : Type u_1
inst✝¹ : NonUnitalNonAssocCommRing A
inst✝ : IsCommJordan A
a b c : A
⊢ ⁅L a, L (a * a)⁆ + ⁅L a, L (b * b)⁆ + ⁅L a, L (c * c)⁆ + ⁅L a, 2 • L (a * b)⁆ + ⁅L a, 2 • L (c * a)⁆ +
          ⁅L a, 2 • L (b * c)⁆ +
        (⁅L b, L (a * a)⁆ + ⁅L b, L (b * b)⁆ + ⁅L b, L (c * c)⁆ + ⁅L b, 2 • L (a * b)⁆ + ⁅L b, 2 • L (c * a)⁆ +
          ⁅L b, 2 • L (b * c)⁆) +
      (⁅L c, L (a * a)⁆ + ⁅L c, L (b * b)⁆ + ⁅L c, L (c * c)⁆ + ⁅L c, 2 • L (a * b)⁆ + ⁅L c, 2 • L (c * a)⁆ +
        ⁅L c, 2 • L (b * c)⁆) =
    ⁅L a, L (b * b)⁆ + ⁅L b, L (a * a)⁆ + 2 • (⁅L a, L (a * b)⁆ + ⁅L b, L (a * b)⁆) +
          (⁅L a, L (c * c)⁆ + ⁅L c, L (a * a)⁆ + 2 • (⁅L a, L (c * a)⁆ + ⁅L c, L (c * a)⁆)) +
        (⁅L b, L (c * c)⁆ + ⁅L c, L (b * b)⁆ + 2 • (⁅L b, L (b * c)⁆ + ⁅L c, L (b * c)⁆)) +
      (2 • ⁅L a, L (b * c)⁆ + 2 • ⁅L b, L (c * a)⁆ + 2 • ⁅L c, L (a * b)⁆)

Tactic:
rw [(commute_lmul_lmul_sq a).lie_eq, (commute_lmul_lmul_sq b).lie_eq,
  (commute_lmul_lmul_sq c).lie_eq, zero_add, add_zero, add_zero]

Result:
A : Type u_1
inst✝¹ : NonUnitalNonAssocCommRing A
inst✝ : IsCommJordan A
a b c : A
⊢ ⁅L a, L (b * b)⁆ + ⁅L a, L (c * c)⁆ + ⁅L a, 2 • L (a * b)⁆ + ⁅L a, 2 • L (c * a)⁆ + ⁅L a, 2 • L (b * c)⁆ +
        (⁅L b, L (a * a)⁆ + ⁅L b, L (c * c)⁆ + ⁅L b, 2 • L (a * b)⁆ + ⁅L b, 2 • L (c * a)⁆ + ⁅L b, 2 • L (b * c)⁆) +
      (⁅L c, L (a * a)⁆ + ⁅L c, L (b * b)⁆ + ⁅L c, 2 • L (a * b)⁆ + ⁅L c, 2 • L (c * a)⁆ + ⁅L c, 2 • L (b * c)⁆) =
    ⁅L a, L (b * b)⁆ + ⁅L b, L (a * a)⁆ + 2 • (⁅L a, L (a * b)⁆ + ⁅L b, L (a * b)⁆) +
          (⁅L a, L (c * c)⁆ + ⁅L c, L (a * a)⁆ + 2 • (⁅L a, L (c * a)⁆ + ⁅L c, L (c * a)⁆)) +
        (⁅L b, L (c * c)⁆ + ⁅L c, L (b * b)⁆ + 2 • (⁅L b, L (b * c)⁆ + ⁅L c, L (b * c)⁆)) +
      (2 • ⁅L a, L (b * c)⁆ + 2 • ⁅L b, L (c * a)⁆ + 2 • ⁅L c, L (a * b)⁆)