Use Billy for combat and exploring new rooms. He has roughly 3.5x the effective health of Rebecca and deals more damage with his handgun.
Conserving resources is critical, as enemies can be bullet sponges. Resident Evil 0 HD Remaster
Rebecca can mix herbs and chemicals, which Billy cannot. She also throws molotov cocktails faster. Use Billy for combat and exploring new rooms
Resident Evil 0 HD Remaster is unique for its "Partner Zapping" system and its lack of traditional item boxes. This guide covers essential strategies to help you survive the Arklay Mountains. Survival & Partner Management Resident Evil 0 HD Remaster
PSA: There's an easy way to beat the last two bosses! "Spoilers"
Survival depends on knowing your characters' strengths and managing them as a team.