Why did Hashem discuss trusting in man?
Radak: It is because Yisrael trusted in Egypt and Ashur. Malbim - "Hoy ha'Yordim l'Egypt l'Ezrah
How does he rely on man?
Rashi: In his plowing and planting. He says, I will seed in Shemitah and eat.
What is "Zero'o"?
Rashi, Targum Yonasan: This is like Ezro (his help).
How does he veer his heart from Hashem?
Rashi: Hashem promised [if you will guard Shemitah] "I will command My Brachah to you" (Vayikra 25:21).
Radak, Malbim: He trusts in man alone. If he trusted in Hashem, and intended that with Hashem's help, a man will help him, this is not evil. Malbim - one who totally veers his heart from Hashem is cursed.