No, the team may not take down the wire/zip line. There are several rules that prohibit that kind of change.
First--it isn't allowed at all.
Rule 14: Mission Models - You may not take mission models apart, even temporarily.
Second--the team isn't allowed to do it by hand. Rule 20: Sending/Handling Things Outside Base
- Your hands may not directly or indirectly strategically change the shape, position, motion, quantity, or other status of things outside Base ...
Third--if the robot does it, then your team can't score points because of doing it.
Rule 34: Model Damage - Any scoring success which obviously depended on model damage is marked scoreless.