All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
The author of Misbaah Az-Zujaajah is Shihaab Ad-Deen Al-Booseeri, Abul-‘Abbaas Ahmad ibn Abu Bakr ibn Ismaa’eel ibn Saleem ibn Qaymaaz ibn ‘Uthmaan Al-Booseeri Al-Kinaani Ash-Shaafi’i.
He was born in the month of Muharram in 762 A.H. He lived in Cairo and continually sought the company of Imam Abdur-Raheem Al-Iraaqi in his old age, from whom he acquired much knowledge; and then he continually sought the company of Ibn Hajar Al-‘Asqalaani and studied at his hands. He also met Ibn Haatim, At-Tanookhi, Al-bulqeeni and Al-Haythami and learned knowledge from them.
He authored many books, among which are:
Fawaa'id Al-Muntaqi li-Zawaa'id Al-Bayhaqi;
Tuhfatul-Habeeb lil-habeeb biz-Zawaa'id fee At-Targheeb wat-Tarheeb;
Ithaaf Al-Khiyarah Al-Maharah bi-Zawaa'id Al-Masaneed Al-‘Asharah.
As regards your question, “What is the status of his authentications? Are they accepted independently or is he in need of support?” As for the Zawaa'id that Al-Booseeri mentioned in his book, he is not their reporter; rather, they were reported by Ibn Maajah . What Al-Booseeri did was collect the ahaadeeth that were only reported by Ibn Maajah apart from the other authors of the six books of Sunan.
Al-Booseeri elaborated on the ahaadeeth that he collected and clarified which are authentic and which are weak, and he kept silent about some of them. But he mentioned in the introduction that the ahaadeeth about which he kept silent are debatable.
So the question should be to what extent the ahaadeeth only reported by Ibn Maajah are authentic. Indeed, the scholars spoke about that; for instance, Ibn Taymiyyah said, “The ahaadeeth that were only reported by Ibn Maajah are inauthentic in general.” This is what Ibn al-Qayyim quoted in Zaad al-Ma’aad.
Ibn Hajar quoted Abu Al-Hajjaaj Al-Mizzi, saying, “All the ahaadeeth that were only reported by Ibn Maajah are weak." Then Ibn Hajar said, 'It is more appropriate to attribute the weakness to the narrators whose ahaadeeth were reported only by Ibn Maajah, not the texts of the ahaadeeth, as I have already mentioned before that they also include saheeh (sound) ahaadeeth and hasan (good) ahaadeeth that were only reported by Ibn Maajah and not by others.'”
Therefore, according to the statement of Ibn Hajar, it is not correct to say whether we accept or reject the ahaadeeth that were only reported by Ibn Maajah; rather there are ahaadeeth that are accepted and there are those which are not. So each of those ahaadeeth should be looked at individually.
Allaah knows best.