What is "Hadarcha Tzelach Rechav"?
Refer to 45:4:3:1-3.
Radak: You will pass and ride on Emes and Anavah of Tzedek. "Tzelach" is to pass, like "v'Tzalehu ha'Yarden" (Shmuel II, 19:18). I.e. when you pass on your enemies and ride, your chariot will not be of pride, rather, of Emes and Anvah Tzedek.
Malbim: Your primary beauty is success not via the sword or war, rather, via riding on Emes. It is as if the horse on which you ride is not of war, rather, of Emes (in investigation), and with Anavah of Tzedek (in deed).
Malbim (Derech ha'Muskal): Your beauty is reaching Emes via investigation.
What is "Anvah Tzedek"?
Radak #1: It is Anavah of Tzedek. Even though Anavah is Samuch, the last letter was not changed to Sov. The same applies to "k'Eifah Se'orim" (Rus 2:17).
Radak #2: It is Anavah and Tzedek. It says Anvah (with a Sheva under the Nun), the same grammatical form as Avlah. The prefix Vov is omitted from Tzedek, like "Shemesh Yare'ach" (Chabakuk 3:11).
Malbim (Derech ha'Muskal): This is intellect that pertains to action. It is obtained via humility - making all Midos of the body submissive to Tzedek.
Why does it say "Al Devar Emes"?
Rashi: This is to rule correctly.
What is "v'Sorecha"?
Rashi: The Torah and Emes that you engage in, it teaches to you war strategy, that your right hand will do wonders. Because it mentioned Talmud Torah in an expression of war, it mentions "Yemincha", which is skilled for war.
Radak: When your chariot is with Emes and Anavah, your right hand will be Toreh (show) to you wonders against your enemies.
Malbim: The military wonders that you could have done via your right hand, via riding on Emes and Anvah Tzedek, you will do them (defeat your enemies) without war.
Malbim (Derech ha'Muskal): What you attain via great exertion of investigation, you will attain instantly via Ru'ach Hashem, without exertion.