The uphill TT comes after the 68 mile ride? Ouch.
Ideally, I think I would try to be in zone 4 (.91-1.05 of FTP ) for the flatter part and zone 5 (1.05-1.20 of FTP) for the climb since it should take <20minutes.
But depending on how the first part of the ride goes that might be optimistic! If possible limit total efforts that are higher than zone 3 to <10 total minutes in this first part of the ride since surges in effort will fatigue you quicker than a steady pace.