Personally, I believe that to be a mistake by Jin Yong that Zhu Ziliu has surpassed Wang Chuyi. Throughout LOCH we learn the following:
Ouyang Ke was often ranked as equal to the mercenaries of Wanyan Honglie (Sha Tongtian, Peng Lianhu, etc.) but also he was also sometimes ranked as equal to Ma Yu, Qiu Chuji and Wang Chuyi. In chapter 11 the part where Yang Tiexin met up with Qiu Chuji again after all those years, we can see that Peng Lianhu, Hou Tonghai and Ouyang Ke combined forces to attack Qiu Chuji. Qiu Chuji held his ground and reached a stalemate with them. If Ouyang Ke was equal to Qiu Chuji, with the assistance of two other peers of himself wouldn't he be able to kill Qiu Chuji rather fast? But that doesn't happen. A poisoned Ma Yu was able to ward off a combined attack of Sha Tongtian and Liang Ziweng (again two martial artists ranked as peers of Ouyang Ke) for a short while.
*1 Qiu Chuji began to lose when all of them (including Liang and Sha) attacked him. Sha Tongtian, someone who was often ranked as equal to Ouyang Ke throughout the novel, clashed palms with Qiu Chuji. Qiu was only a bit shocked to see that this bald man could handle his palm attack, Sha's arm felt numb and pain, Qiu felt nothing. Sha Tongtian engaged Qiu Chuji again with bare hands, Qiu Chuji whisked him on his head with his fingers; leaving red imprints on the bald head of Sha. Qiu Chuji was able to force Peng Lianhu to drop one of his Judge's brushes in a few bouts. It would seem that one on one, those mercenaries of Wanyan Honglie are inferior to Qiu Chuji (and subsequently Ma Yu and Wang Chuyi as well*2)
*1: This happened before Ma Yu was poisoned.
*2: Ma Yu, Qiu Chuji and Wang Chuyi were the three strongest of the Seven Masters. Ma Yu's fighting skills and technique wise profiency were said to be a bit inferior to Qiu Chuji and Wang Chuyi. (Although, I think he makes up for that with more stronger and abundant internal energy. Jin Yong never said that Ma Yu had the strongest or deepest internal strength compared to the others, but he did always stress that Ma Yu had deep and profound energy more than he did with the others). Suffice to say that all three of them were evenly matched (in my opinion).
My look at this is: How can Ouyang Ke be equal to the Seven Masters, and also to those mercenaries? Did Jin Yong mean that they belonged to the same class category? That is possible, but as equals that would seem untrue. Lav ranked the weaker masters of Quanzhen as equals to the mercernaries (including Ouyang Ke), while Ma, Tan, Liu, Qiu, Wang were a notch better.
If you read some of Laviathan's posts on ranking LOCH and ROCH mid-level fighters in the past, you often would see that in his eyes Sun Bu'er (or Hao Datong)= Ouyang Ke. And later on in ROCH Hao and Sun = Da Er'ba and Huo Du.
Ma Yu, Qiu Chuji and Wang Chuyi's martial arts level should be closer to Mei Chaofeng than Ouyang Ke and the other Jin Empire mercenaries.
Ma, Qiu and Wang roughly Mei Chaofeng. Ouyang Ke is not a match for Mei.
On top of that, Ma Yu and Qiu Chuji were able to do some things that impressed Huang Yaoshi a bit. Qiu Chuji was able to whisk Huang in the chest with his sleeve, but that was because Huang underestimated Qiu. But nonetheless, not bad for old Qiu. Ma Yu counter-attacked Huang Yaoshi's attack during their battle in Misty Rain Pavilion. Huang Yaoshi stormed at Ma, assuming that Ma would not be able to do anything but move away from his key position in the formation. But Ma Yu raised his sword and counter-attacked. His technique was steady and firm, generated with powerful internal energy. Huang Yaoshi moved away and genuinly praised Ma Yue saying:"Worthy of being the Quanzhen head disciple!"
Back to Wang Chuyi, maybe the clue in defeating Zhu Ziliu lies in either a more profound and deeper understanding of martial arts and a more aggressive fighting style a la Qiu Chuji. Or the other key factor in defeating Zhu Ziliu is powerful internal energy. Most readers, including me, believe that Ma Yu has more internal power than the other masters. So, perphaps Wang Chuyi maybe all-round equal to Qiu and Ma at the time of ROCH. However, he still fell behind in the martial arts proficiency area compared to Qiu and the internal energy wise inferior to Ma Yu leading to him being weaker than Zhu. The best explanation would be a mistake by Jin Yong. Because it is implied and believed that Ma, Liu, Qiu and Wang are superior to Li Mochou. Zhu Ziliu is equal to Li Mochou, but if that's the case how can Wang be inferior to Zhu again. Unless we have the A > B, but B = C, but then C > A equation.
Li Mochou should be weaker than the four masters of Quanzhen (Ma Yu, Liu Chuxuan, Qiu Chuji and Wang Chuyi. Li Mochou was afraid of those old Taoist priests of the Quanzhen school and she said that if she had studied and mastered the Art of the Jade Maiden she would not fear them in combat. The only Masters she met were Liu Chuxuan, Qiu Chuji, Wang Chuyi and Sun Bu'er. As we know that Sun Bu'er is not a match for Li Mochou (and Huang Rong) and she was also defeated by Li (although not in a very fair match but nevertheless defeated), the old Taoist priests she feared in combat were Liu, Qiu and Wang. We know that Ma is at least as good as Liu, Qiu and Wang, so it is likely Ma is superior to Li Mochou too.