Note:
Apparantly this also unlocks for everyone else in the lobby when every zipline has been used at least once by one or more players. It will NOT unlock for players who join in later when all of the ziplines have already been used, no matter which ziplines they ride.
There are 4 ziplines around the map. You must jump up near the zipline start to ride the zipline. A prerequisite is that you have the part of the map opened, where the zipline goes to.
The first 3 and easiest ziplines can be found starting from the roof of the starting cabbin. You will first need to make your way to the mines, either via the recreational zone or via the wolf camp, to turn on the power. Once you have the power on, you can access the attic of the starting cabbin. There are 2 ziplines on the right hand side of the roof (one towards the recreational area and one towards wolf camp), and one on the left hand side.
The fourth and final zipline will take some time to reach. It is located on turtle island. You will first need to build the boat, which consists of 3 pieces, which spawn in fixed locations.
-One part spawns upstairs in the starting area, in the same room as Tuff Nuff. It lays on the right hand side when you enter that room, against the wall.
-One piece is in the mess hall, laying against a pillar in the center.
-One piece is in the recreational area, on the side against some white pieces of cloth, which are part of a market stand.
How to build the boat and Pack a Punch:
Where to find the ziplines:
After you've used the fourth zipline the achievement will unlock.