"The six ministers were quite pleased with the preface you wrote, and once the Prime Minister has reviewed it, it can be presented to the Emperor." Essentially, once it's presented to the Emperor, he wouldn't oppose it.
Zhang Hai also knew that Gu Chengyu and the Prime Minister had some issues, so he didn't mention who wrote it. If the Emperor summoned him because of this, he would directly explain to the Emperor.
But if the Chief Milliner wants to take credit for this task, he would have to confess to the Chief Milliner.
As soon as Gu Chengyu heard of Chief Minister Xia, he worried that the old gentleman would reject the preface upon realizing it was written by him. Don't assume because he is the Prime Minister, he wouldn't stoop to such matters.
If Xia Qing didn't have Min Feng as a disciple, he might not be interested in such a trivial achievement.
