It was strange enough to throw many people off. Remember how terrifying Mui Chiu Fung was during LOCH to anyone who wasn't a Great or late-LOCH Gwok Jing?
In fact, quite a few people at the Shaolin "Lion-Taming" Convention had superior martial arts to Chow Chi Yerk (including Mo Dong Heroes # 1, 2, and 6). Given sufficient time to figure out her limitations, they should be able to defeat her. CCY's limited time to train with the manual meant that she only was able to achieve the illusion of great ability. When tested against Cheung Mo Gei and the three Do-generation Shaolin elders, she was completely overwhelmed by their superior power and could not even enter the perimeter of their struggle.
Well I think only 1st and 2nd Hero was clearly stronger than ZZR (post 9 Yin) while 4th/6th Hero might be only equal with ZZR at best..
I think the 9-yin, especially with the sanskrit portion, is very neutral internal energy.
There is no evidence that it is especially "yin" based given that:
GJ uses the most "Yang and fierce of Palms" with no problem using 9-yin and other taoist internal
H7G also has the 9-yin sanskrit portion which doesn't seem to impact his XL18P-- even though he had specifically made a comment about how HYS and others wouldn't be able to learn/utilize XL18P given yin nature of their internal-- thus imlying the neutral and multifaceted nature of 9-yin
1-Deng also has taoist internal XTG which is similar to 9-yin (he technically also has 9-yin Sanskrit internal)-- and he has no problem using a technique called Yi YANG finger