rw [add_zero] at hc3
case right.succ.intro.intro.intro.intro.intro
a b✝ c : ℤθ
b : ℕ
h1 : (↑(unit ^ (3 * -↑b))).f % 3 = 1
h2 : (↑(unit ^ (3 * -↑b))).g % 3 = 0
h3 : (↑(unit ^ (3 * -↑b))).h % 3 = 0
p : Nat.succ b = b + 1
w : ↑(unit ^ (3 * -(↑b + 1))) = ↑(unit ^ (3 * -↑b)) * ↑(unit ^ (-3))
c1 : ℤ
hc1 : (↑(unit ^ (3 * -↑b))).f = 3 * c1 + 1
c2 : ℤ
hc2 : (↑(unit ^ (3 * -↑b))).g = 3 * c2
c3 : ℤ
hc3 : (↑(unit ^ (3 * -↑b))).h = 3 * c3 + 0
⊢ (↑(unit ^ (3 * -↑(b + 1)))).f % 3 = 1 ∧ (↑(unit ^ (3 * -↑(b + 1)))).g % 3 = 0 ∧ (↑(unit ^ (3 * -↑(b + 1)))).h % 3 = 0
case right.succ.intro.intro.intro.intro.intro
a b✝ c : ℤθ
b : ℕ
h1 : (↑(unit ^ (3 * -↑b))).f % 3 = 1
h2 : (↑(unit ^ (3 * -↑b))).g % 3 = 0
h3 : (↑(unit ^ (3 * -↑b))).h % 3 = 0
p : Nat.succ b = b + 1
w : ↑(unit ^ (3 * -(↑b + 1))) = ↑(unit ^ (3 * -↑b)) * ↑(unit ^ (-3))
c1 : ℤ
hc1 : (↑(unit ^ (3 * -↑b))).f = 3 * c1 + 1
c2 : ℤ
hc2 : (↑(unit ^ (3 * -↑b))).g = 3 * c2
c3 : ℤ
hc3 : (↑(unit ^ (3 * -↑b))).h = 3 * c3
⊢ (↑(unit ^ (3 * -↑(b + 1)))).f % 3 = 1 ∧ (↑(unit ^ (3 * -↑(b + 1)))).g % 3 = 0 ∧ (↑(unit ^ (3 * -↑(b + 1)))).h % 3 = 0