After falling off the zipline and losing your weapons, make your way through the building until you open a door. Just after this there will be a body with some arrows on it. Pickup the arrows and move into the corridor and jump through the window on the right side, then sneak your way into the room on the right. The Recurve Bow can be found next to some wooden crates.
Play through the mission until you need to use the Zipline again, this is just after encountering an enemy on a turret in a watchtower. Go on the Zipline and use the Recurve Bow to eliminate one of the enemies on the other side. Try and do it with your first shot so that you can revert to last checkpoint if need be.
If you are still struggling, feel free to use this video as a reference.
Hope this helped.