var camSpeed = 10;

function Update ()
{
var camTrans = Camera.main.transform;

camTrans.Rotate(0, Input.GetAxis("rotate"), 0, Space.World);
camTrans.position += new Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical")) * Time.deltaTime * camSpeed;
camTrans.position += camTrans.TransformDirection(new Vector3(0, 0, Input.GetAxis("Zoom")) * Time.deltaTime * camSpeed);
}