Collision Causing Lag?

I have a game in which zombies chase the player and destroy it by touching the character.And destroy zombies by shooting them. Anyway every thing works but when the zombies get close to eachother they collide causing terrible lag. I know this because I took the colliders off no lag what so ever.

How can I fix this without getting rid of my Colliders(as they are needed for the game to function)!?


is it just the colliders? or are you having a script run when it collides. also if you're using a mesh collider, either use a low poly mesh, or use a box collider, etc. if you don't need accurate collision.