This stage is basically an endurance match against Zombies with Papaou in the back serving as the “Immovable Object” preventing you from ragaining ground. The primary threats here are the Zapies and Zang Roos spawning throughout the stage. Chief, Housewife, and Musashi do well at keeping these threats under control, especially Chief due to his ability to nearly 1-shot the Ariants that also appear here. Keep resurfacing burrowed Zang Roos and eventually the Zombie spam will die down and allow you to chip down Papaou and finish the stage.
Beating this stage unlocks Areas 17-19 of Ashvini Desert, the final stretch before what may be the end of Behemoth Culling…