Then he said to the king: Translators will do well to remind the reader that Zerubbabel is the speaker here. Good News Bible and Contemporary English Version say simply “Zerubbabel replied,” which is a helpful model. Good News Bible and Contemporary English Version also begin his words with “Your Majesty” to show respect to the king.

Remember the vow which you made to build Jerusalem …: No other source is known for the notion that Darius vowed to rebuild Jerusalem, or that Cyrus before him had promised to return the sacred utensils of the Temple to Jerusalem. In 1 Esdras, however, this is the reason given for Darius’ sending the Jews back to their land. Zerubbabel, who will be a leader in the return, has, by establishing the importance of being reliable, challenged the king to be true to a vow he had earlier made. Remember the vow which you made may be rendered “Your Majesty, please don’t forget the strong [or, solemn] promise you made.”

In the day when you became king: Contemporary English Version places this clause before the previous one by saying “Your Majesty, the day that you became king, you made a solemn promise to rebuild Jerusalem.”

And to send back all the vessels that were taken from Jerusalem: It should be made clear that the vessels were the sacred objects from the Temple in Jerusalem that the Babylonians had stolen (see 1 Esd 1.41). A model that does this is “and to return all the sacred things [or, treasures] that had been taken from the Temple in that city by the Babylonians.”

Which Cyrus set apart when he began to destroy Babylon: For Cyrus, the first Persian king, see the comments on 1 Esd 2.1-2. Instead of he began to destroy Babylon, the Greek text has “he vowed to destroy Babylon” (see Revised Standard Version footnote). Revised Standard Version changes the Greek text for its reading. Good News Bible and most other translations follow the Greek text. Translators may follow either reading. In this context Babylon refers to the capital city of Babylonia (see the comments on 1 Esd 1.40). This clause may be rendered “which King Cyrus had saved when he began [or, promised] to destroy [the city of] Babylon.”

And vowed to send them back there may be expressed as “and promised to return them to Jerusalem.”

Good News Bible provides a helpful model for these verses. Another possible model is:

• 43 Then Zerubbabel said to the king, “Your Majesty, please don’t forget the solemn promise you made on the day that you became king. You promised to rebuild Jerusalem. 44 You also promised to return all the sacred things [or, treasures] that had been taken from the Temple in Jerusalem when the Babylonians destroyed that city. King Cyrus saved these treasures when he began* to destroy Babylon, and he promised to return them to Jerusalem.”
* began; Greek manuscripts have promised.

Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on 1-2 Esdras. (UBS Helps for Translators). Miami: UBS, 2019. For this and other handbooks for translators see here.