have a question.

If a member/s are in an immortal clan and quits their clan and then joins a shadow clan the same day during the middle of the week, can the member/s then be an immortal if the shadow clan they join wins the rite of exile that weekend?

No, they can't. They will have to wait for next cycle.
If you (as a Shadow Clan) do become the next Immortals, the Immortals that joined your Shadow Clan will be automatically kicked.

I enjoyed shadow more than immortal,

The daily quests are very boring and in hell 3 you have to find groups. Anyway, benefit of immortal is nice. We won exile 6-2 and we will keep doing so