1)
Seeing as the Mishkan comprised two levels of Kedushah (the Kodesh and the Kodesh Kodshim), why does the Torah write "Vehayah ha'Mishkan Echad"?
1.
Seforno: Because the two parts correspond to different levels of angels, which work in unison to perform the will of Hashem. 1
2.
Rashbam: Because with reference to the bottom set of curtains, the Torah is simply saying that the two sets of five curtains became one via the series of loops and hooks. 2
1
As the Pasuk writes in Yeshayah (6:3) "Vekara Zeh el Zeh ve'Amar Kadosh!" (Seforno).
2
As is evident from Pasuk 11, which uses the same expression in connection with the goats-hair curtains.
