1)
What has four faces?
1.
Radak: Each Keruv.
2)
What is the face of a Keruv?
1.
Radak: It is a Ravya's (child's) face, In Bavel, a child is called Ravya.
3)
Above, one of the four faces was an ox. Here there is a Keruv in place of it!
1.
Refer to 10:1:2:1.
2.
Malbim: Now he saw the Chayos receiving from Olam ha'Kisei, and conducting miraculously. There is no Din above; mercy overpowers. Therefore, he did not see an ox on the left, rather, a Keruv - there, also the left arouses mercy. There was influence from above to burn the Beis ha'Mikdash, but the Midah was mercy, to finish His anger on wood and stones. Therefore, the first face he saw was on the left - a Keruv.