Following are a number of back-translations as well as a sample translation for translators of Isaiah 9:7:

• Kupsabiny: “His kingdom shall go on forever,
  and the peace of his rulership shall never end.
  He shall sit on the chair of David,
  and be ruling instead of him.
  He shall guard and build his land,
  stepping/focusing on truth and gentleness,
  from then and forever after.
  The God of authority shall make
  those words come true.” (Source: Kupsabiny Back Translation)
• Newari: “His government and the flourishing
  of [his] peace will never end.
  He is the king who comes after king David.
  Standing strong for the sake of justice and righteousness,
  He will reign from today forever.
  The passion of the LORD Almighty
  of all will accomplish this.” (Source: Newari Back Translation)
• Hiligaynon: “Without end the progress of his ruling, and it always has peace. He will-inherit the kingdom of David. He will-establish it and will-reign-over with justice and righteousness without end. The LORD Almighty will-make-sure that this will-be-fulfilled.” (Source: Hiligaynon Back Translation)
• English: “His rule, and the peace that he brings/causes, will never end.
  He will rule fairly and justly ,
  like his ancestor King David did.
  This will happen because the Commander of the armies of angels greatly desires that it happen.” (Source: Translation for Translators)