What is the meaning of "Yibolel"?
Rashi: Efrayim will be Mevulbal (mixed) in Galus among the nations 1 . Radak - this is like "Ki Sham Balal Hashem Sefas Kol ha'Aretz" (Bereishis 11:9). Hashem divided them from the nations, and they mixed with them and did like their deeds!
Malbim: This was due to killing its kings. Menachem called to Melech Ashur to help solidify his kingship. When Pekach killed Pekachiyah ben Menachem, Melech Ashur came to wage his quarrel, and in passing he waged the quarrel of Melech Yehudah, and exiled Eretz Naftoli. After, when Hoshe'a ben Elah killed Pekach, he came against Hoshe'a, like I explained above (refer to 7:3:1:4).
What is the comparison to "Ugah Bli Hafuchah"?
Rashi citing Targum Yonasan: It is like a cake (baked on coals) ? it was eaten before they turned it over.
Radak: A cake baked on coals, if they do not turn it over, it burns on the bottom and does not bake on top. So is a counsel that is not correct, when they do not reverse it from matter to matter, until they settle it properly. So was Efrayim's counsel to serve the calves and other gods ? it did not distinguish and choose well.
Malbim: Because it used the metaphor of an oven, it compares Efrayim to a cake not baked in an oven heated with the fire of their anger, rather, on coals. One must flip it over several times so it is cooked on each side. If one does not flip it, there are two problems. (a) The bottom side near the coals it get burnt. (b) The top does not get baked and is improper to eat.