Is Yet Another Zombie Survivors Co-op or Crossplay?

Short answer: not officially confirmed in this snapshot

The reviewed Steam and PlayStation listings describe single-player or one-player play. The official sources checked for this page do not provide a confirmation of online co-op, local co-op, or crossplay.

That means the responsible answer is unconfirmed, not a confident “yes” or “no” based on a community page, a shared platform listing, or a search suggestion. A future official update can change the answer.

What a player should verify

1. Check the current store feature list for the platform you use.
2. Look for an official developer announcement that names co-op or cross-platform play.
3. Do not infer crossplay merely because the game is on PC and consoles.

Why this is a separate intent

“What platforms is the game on?” helps a player decide where to buy it. “Can I play with someone?” is a different purchase and planning question, so it belongs on this focused answer page rather than being hidden in a general platform list.