@Der:
Can a destroyer move through a zone containing an enemy submarine or end its move in the same zone as an enemy submarine during the non-combat move phase?
Any ship can. Subs never block movement.
The special rule that you’re confusing is exactly the opposite - Subs can move through and into any hostile seazones on combat or noncombat that do not have a destroyer and during noncombat they can choose to move into a seazone that has a destroyer, even though it won’t amount to combat. Quite simply, they can move into or through any seazone at any time, but are stopped immediately with an enemy destroyer.