I am reconsidering the timeline of fulfillment of Zephaniah. My main point I was making is that the nations mentioned in Zephaniah pretty much were destroyed, at least within hundreds of years after Christ. This then means the fulfillment would have had to happen while those nations existed. Consequently, a yet-future fulfillment is not logical. People should not interpret this prophet as yet-future events.
My argument primarily was against a yet-future fulfillment. I consequently focused on the fit of the prophecy fulfillment to the first-century destruction of Jerusalem and the temple. But there is a possibility that the Babylon attack on Jerusalem was the fulfillment. The destruction of Moab fits in that era.
One issue with this being fulfilled in the Babylon conquest is that Kush was not attacked, so Zeph 2:12 seems like the first century CE. Also, Zeph 3:15-17 has the removal of the judgments against Jerusalem. Also, v15 says the king is the Lord will keep them from future evil. This is what Christ Jesus did.
In this first-century fulfillment, the earlier judgments (Moab, Assyria, etc) on nations may have represented earlier judgments of nations that would be underlying history as background for the completion of judgments in the Levant and broader areas upon Christ's era. I think pertinent here is that Zeph 3:9-10 ultimately reflect the gospel's reach to the nations through Christ Jesus.