Zhoudi knew that Wang Tong was a force to be reckoned with, since even the Dark Lord was not able to overcome him. He was certain that he could not stand a chance while fighting against the latter one on one. However, he also realized that he didn't have to. He was in space, and space battles rarely involved personal combat.
He lamented on how stubborn the Dark Lord had been to meet the human devil head-on. If Zhoudi were him, he would drag out the war and avoid direct contact with Wang Tong. What use would Wang Tong be if the Zergs slowly killed off the rest of the humans until there were none left?