The problem I'm seeing is that Meizhen and Sun aren't static. Even if we do somehow become strong enough after breakthrough to stand up against the monster trio as they are NOW. Well... they've been in Green for a couple months more than us, and they're constantly growing stronger too. They're not static in strength.
By the time we're strong enough to match up against current Bai Meizhen and Sun Liling, Sun and Bai are still gonna be stronger than us. It's supposed to take us a couple of years or lot of luck/moon assistance to actually be completely at their level.
I'd say their biggest advantage are their spirit beasts. Zhengui is
very unlikely to get to Green before the tournament, I think, and even if he does he'd still have much, much less time to learn to express his abilities than their own spirit beasts.
Monster themselves, though, we could thereotically close a large part of the gap. Taking Meizhen as an example, she got to late yellow week 5, we got there week 24. She had mastered 4 arts to the limit of her cultivation and 4 others to a limited degree week 15, we should have, if we are lucky, mastered 5 arts to the limit of our cultivation week 35 and 4 others to a limited degree. She broke through to green week 19, and if we are lucky we should break through week 37. That's roughly 18 weeks behind her in pure cultivation at first, and now we are catching up both in numbers of arts at equivalent level but also cultivation to week 37 (maybe even better, as we'll have 6 arts mastered to the limit of our cultivation when breaking through).
While Meizhen herself has the same access we do to superior sites (Black Pool, hopefully Mystic Vale), the other monsters should not, and CRX lags a bit behind Sun Liling, cultivation wise. If we play things right, I
think we should be able to get, by the tournament, at the equivalent of Sun Liling week 45 or so.
So... she would still be significantly stronger than us, but considering how cultivation take longer and longer, there are hopes that she would not have arts to Foundation Green, but rather just have more arts to Appraisal than us.
Obviously, all of this depends on how good our breakthrough is, how long it takes to get to appraisal (and if it takes too long, it might not be worth it), and so on.