This was an extremely long level and was filled with tough enemies and also massive amounts of bullets, some of them being impossible to dodge. While the player's health bar is sturdy, it is not built to deal with this massive onslaught. Prepare to use a continue when the Arbiter-X is reached.
The player must have very good reflexes to dodge the bullets due to their numbers. Even so, the Arbiter-X at the end had an impossible to dodge attack pattern and it is impossible to avoid damage there. The player just had to make sure their health bar is as full as possible when they reach there, as up to that point it was possible to dodge all of the bullets if the player's reflexes are very good.
Only choose the multi-directional team. If you choose anything else, it will be near impossible to win because only the multi-directional team has enough firepower to destroy the bosses.
The following strategy uses the multi-directional team as it is the only team that can beat this level.
The Rotobaga should generate enough firepower to defeat the first few zombies. Once you defeat the two Flying Gargantuars coming at the same time, you should gather enough points to upgrade into a Starfruit.
Make sure you have full health before reaching the twin Zombie Fighters. If you don't, reset because you'll most likely lose.
Once you reach the Zombie Fighters, it will be amassed with lots of Lightning Gun Zombies, Conehead Pilot Zombies, and Buckethead Pilot Zombies so defeat them as fast as possible or they will shred you. Then, concentrate on dodging the bullets and defeating one of the fighters. The fighters have two attacks, one being a swirl consisting of yellow, large bullets and one being a quick, small bullet attack. To dodge the first, go between the gaps and when it uses it's second attack, stay as far as possible. Once you defeated one fighter, it's easy. After defeating both fighters, you should be able to gather enough points to upgrade into an Oak Archer.
Midway you should be able to gather enough points to upgrade into a Coconut Cannon Quickly. It shoots in only one line but it can do massive direct and splash damage and will take care of the regular enemies in seconds.
Then you will see a Double-Cabin Aircraft Zombie. The Double-Cabin Aircraft Zombie is easier than the fighters at the start but after a while it will mix the fighter's 2 attacks and will be difficult to dodge. After fighting this mid-boss, you should have less than a quarter of health left.
After that, regular enemies will appear in masses so watch your step.
Finally you will reach the final boss, the Arbiter-X. With a remaining HP this low, it is possible, but very hard to defeat the Arbiter-X without paying at least 1 continue, so try to kill as much of the accompanying zombies as quick as possible so you only have the Arbiter-X to worry about. Arbiter-X seems easy at first, but then it will make two patterns that are near impossible to dodge. Defeat it as fast as possible before it kills you again. With the Coconut Cannon, you should be able to barely make it.
The Arbiter-X's bullets do not disappear after its defeat, so watch out for collateral damage.