Does it support multiplayer?
The current Steam store page lists the game as Single-player. The official Full Release - Version 1.0 announcement used for this project does not provide verified evidence of an online multiplayer or co-op mode. Based on those sources, this page cannot say that Yet Another Zombie Survivors supports multiplayer or cooperative play.
The word squad refers to the in-run group of characters and build decisions in the available game description. It should not be translated into a promise of multiple human players. If a future official update adds co-op, the store feature list and release notes should be rechecked before this answer changes.
What to verify before buying for a group
If multiplayer is the reason you are considering the game, use the Steam feature list and the newest official update notice as the decision gate. A community discussion, a screenshot, or a phrase such as team or squad is not enough to establish a network mode. Keep the question narrow: human-player co-op, local co-op, and a single-player team system are different claims.
- Look for an official multiplayer or co-op feature label.
- Confirm whether the mode is online, local, or only an in-run squad system.
- Check the date of the newest official announcement before relying on an old answer.