Are the enemies in this asset in unity store fully optimized so that there are no frame rate drops when there are many enemies? And secondly, are the enemies fully compatible with 2D NavMesh?
Viewing post in Zombie Rural - HD Isometric Tileset comments
If you purchase the asset through the Unity Asset Store, it includes an example scene that demonstrates the tiles and zombie characters in action. The scene uses standard Unity animators and no additional performance optimization has been applied.
The example scene is not intended to function as a game template. Its only purpose is to showcase the graphics. It does not include pathfinding, and no performance testing has been done on the scene.
For best performance in an actual project, I recommend creating your own animator setup and writing your own gameplay code around the characters, tailored to your specific needs.