High Wire Act Achievement Guide | Call of Duty Modern Warfare 3
Call of Duty Modern Warfare 3 (2023) High Wire Act Trophy Guide / Achievement Guide - Kill 10 enemies while using a zipline [Bronze]
This can easily be farmed in Mission 3: Reactor. At the start of the mission, land on the roof on the right, next to the first helicopter (main objective). There's a zipline between two roofs over the first helicopter. On this roof you also find the "Ascender" which you must collect to use the ziplines.
Now keep going back and forth and this zipline and kill enemies while using the zipline. It counts 10 kills total across multiple zipline uses (doesn't need to be in 1 zipline ride). It keeps counting even if you die / restart checkpoint / restart mission, so this can be farmed too. If you run out of ammo simply collect the weapons from dead enemies or use an ammo refill box