Zombie Army 4: Where to Find All Upgrade Kits in Rotten Coast

Zombie Army 4: Dead War is the latest game in the Zombie Army series, a spin-off of the Sniper Elite franchise and created by Rebellion Developments. It's releasing during a relatively quiet period in gaming, which can often help draw more sales and eyes. Zombie Army 4's reviews have been about average for the franchise, guaranteeing that longtime fans should have a good time with it.
Zombie Army 4: Dead War uses an upgrade kit system, with said kits being hidden throughout the levels. The game gets progressively more difficult, so without these kits, and without using them to upgrade weapons and gear, it will be quite challenging to complete the high-level areas.

Zombie Army 4: Dead War will take about 10-12 hours to beat, but that amount will vary depending on the difficulty level that players choose. Additionally, without finding the upgrade kits, that amount could skyrocket.
Each level in the game has upgrade kits to find. The "Rocket Coast" level has five hidden upgrade kits. Here is where to find them, meaning what part of the mission it takes place on and how to find them on the level itself (in most cases, the upgrade kits are found off the beaten path):

Head to The Resistance Compound

During the first chapter of the game, when the top right states that the current objective is to "Head to the Resistance Compound," follow the road to the far end and towards the right. Clear out the remaining zombies and at the end of the road, there will be a small shack. Inside the small shack, there will be an upgrade kit on the brown table.

Destroy The Zombie Half-Track

During a section in chapter two, the goal is to keep a sniper alive atop a tower. If the objective is met, if the sniper is kept alive from zombies and from a very challenging tank below (which probably won't crack anyone's top 10 tank missions) a safe will open up right behind the sniper. An upgrade kit is behind him and inside the safe.

Get to The Safe Room

While still in chapter two the objective will tell players to "Get to the Safe Room." As much as finding some safe space and avoiding the creepiness for a moment may sound nice,  bypass this and follow the road past the safe room, hugging the wall to the left. The first available house to the left, with an open door, is where the upgrade kit will be found. Go into the house, up the flight of steps. On top of the counter on the second floor is where the upgrade kit can be found.

Re-Align The Communication Dish

The fourth upgrade kit is found while working on the "Re-align the Communication Dish" objective. In the swampy area, follow the swamp to the left and there will be a house/shack up against the water. Inside the shack is where a useable buzzsaw can be found, which probably doesn't hold a candle to Nazi sharks, along with the upgrade kit.

Exit The Cellar

While working on the "Exit the Cellar" objective, directly after fending off a buzzsaw wielding enemy, around the corner and through some gassy catacombs to the left there will be an upgrade kit on a barrel, the final for "Rotten Coast" in Zombie Army 4: Dead War.