I don't really understand what this sentence means. Can anyone help shed some light for me?
"Shed some light" that is an unusual phrase. Sure, I can drop some extra light I have on you, just don't go wasting any photons, OK?
One could consider the act of thinking as low effort or high effort. Low effort is riding a bike, you do not have to do much thinking to do that. On the other hand high effort thinking is learning this language with all its nuances and practically requiring us to rewire our brains. When you are engaged in a high effort, there is no doubt you are thinking, your brain has to be actively engaged, like the warp drive on a starship.
Yes, in Vietnamese we say "Đó là một nỗ lực lớn." That sentence (Đó là một nỗ lực cao) is said by Duo (not a Vietnamese person).
Maybe this is an attempt to translate the English idiom "that is a tall order", implying that the task requires an unreasonable amount of effort.