The Talmud in Gittin 88a says that Israel was only destroyed once it had seven courts that worshipped idols: Jeroboam son of Nebat's, Baasa son of Ahija's, Ahab son of Omri's, Jehu son of Nimshi's, Pekah son of Remalia's, Menahem son of Gadi's, and Hosea son of Elah's.
Rashi explains how the Talmud arrived at this number. Each 'court' coincides with each family of the Northern Kings, of which there were technically nine, but he excludes Shallum son of Jabesh, Zecharia, and Zimri, who did not rule for a full year.
Why did Rashi feel the need to exclude Zecharia from the Idolatrous courts?
עיון יעקב says that Zecharia was worse than any of the other kings in Jehu's line, based on 15:9's extra phrase, כאשר עשו אבתיו, as his father's did. So I guess he made a new court to accomodate his wickedness, but it didn't last a year. However, this doesn't sit so well with me, because it seems that if this were the case, Rashi should have said something about this somewhere, though, instead of just assuming we knew.
Do any other sources discuss this and bring an alternative explanation?