Thus, with his King Level BOSS identity and strength, Zhang San had an easy time dealing with the minor Monster invasions. However, once those powers regrouped, they'd likely send their real core experts. And when that time came, Zhang San's days would not be so easy anymore.
But Zhang San didn't concern himself too much with that. His resistance against the minor Monsters was simply because he had received orders from Zhou Tian to guard that Domain. To be honest, while Tian Zhou's defeat wouldn't benefit him at all, Zhang San was far less concerned about those powers' Invasions than Zhou Tian was.
So, even though he knew that so many Monsters attacking Zhou Tian's Territory at once was not a good sign, all Zhang San did after reporting to Zhou Tian was then to refrain from taking any other Action at that time.