This is a joint work with Koji Tasaka. I will first introduce a non-canonical algebra isomorphism proved by Francis Brown. Using this isomorphism, we can give another proof of Euler-Zagier decomposition formula of double zeta values of odd weight, which was originally first proved by Zagier in his Annal’s paper in 2012. According to the parity result, we are expected to have such a formula also in higher depth case. In this talk, I will give a proof about the decomposition formula of (motivic) triple zeta values of even weight. The proof uses the duality between Ihara coaction and Brown’s derivation operator. Our result is proved in the motivic setting, while the statement in a recently paper by Erik Panzer is only for the classic triple zeta values.