This question has two parts:
1- Did both of these surah's revelaed regarding the same event in Mekkah?
2- If so, can you provide background of these ayahs?
I exercise inquiry on four commentaries. First I will point to which is explained by some commentaries under above questions and consequently refer to some points.
First we concerned with the first verse of Al Naba:
Allame Tabatabei in Tafseer Al Mizan Says that:
This surah concerned with the day of judgment and resurrection and its descriptions. Allameh Tabatabei says in continue: some believes that the word of Naba means that Quran but Allameh According to the context of Surah reject this opinion. Also some believes that Naba refres to proving of God , its adjectives, heaven but this opinion too rejected by Allameh.(p.257) according to Allameh, the surah revealed on those who rejected the day of judgment.(p.258)Ayatollah makarem Shirazi says that: some men of commentary believe that the word Naba refers to the Imamate of Ali-peace be upon him. In this case he refers to three narrations in emphasis of the attitude. For example Imam Sadiq Says that: Naba is Imamate and Velayat(leadership of Ali).
There is no challenge among men of commentary on being Meccen of Surah Al naba. But there is challenge in Surah Al Marej .Allmeh tabatbaei believes that some verses of The Surah revealed in Medina.he says that: "the context of the Surah concerned with Munafeqin not Infidels, those who accompanied with the holy prophet in Medina. He says: Munfeqin in fact aacoording to Suarh Tobah are infidels".
Allameh Tabtabei believes that the surah Al Marej revealed in medina in term of its content and context. He also refers to the background as follow: "this surah revealed in response to one who asked of god if this is right-it refers to election of Imam Ali as successor of the holy prophet during the Ghadir Khom- then send me your torment"(Anfal Sureh, verse.32)
Ayatollah Makarem Sirazi says that: most Sunni men of commentary refer to this event as background to which this surah revealed. Allameh Amini also refers to 30 of them. Some of them are as follow:
تفسير غريب القرآن ((حافظ ابوعبيد هروى )).
تفسير شفاء الصدور ((ابوبكر نقاش موصلى )).
تفسير الكشف و البيان ((ابواسحاق ثعالبى )).
تفسير ابوبكر يحيى ((القرطبى )).
تذكره ابواسحاق ((ثعلبى )).
كتاب فرائد السمطين ((حموينى )).
كتاب ((دررالسمطين )) ((شيخ محمد زرندى )).
تفسير سراج المنير ((شمس الذين شافعى )).
كتاب ((سيره حلبى )).
كتاب ((نور الابصار)) سيد مؤ من شبلنجى )).
و كتاب شرح جامع الصغير سيوطى از ((شمس الدين الشافعى )).
I think that if we put together these commentaries we can concluded that this verses refers to same event which is Imamate of Ali.
Allameh Tabatabei, Al Mizan
Ayatollah Makrem Shirazi, Tafsire Nemmoneh