1)
What is the grammatical form of "Esayu"?
1.
Radak: It is a command. The last letter of the root is silent, like "Be'ayu" (21:12). There is a Tzeirei under the Aleph, lest one rush its pronunciation.
2)
Why does it mention Chayso Sadeh and Chayso Ya'ar?
1.
Rashi: Chayas ha'Ya'ar refers to the Giborim of the Bavliyim who were stubborn. It is stronger than Chayas ha'Sadeh.
2.
Radak: All Chayos of the field and land will come to eat the dead bodies of Machaneh Gog and Magog. And so it says "Emor l'Tzipor Kol Kanaf ul'Chol Chayas ha'Sadeh Hikavtzu
