That one took a while. The gimmick of the Red Cliffs scenario is a bunch of naval outposts with invincible production buildings that you capture by damaging the central tower. Trying to fight on water 1 against 2 never worked since the outposts on the opposite shore could easily be recaptured with siege rams, so the winning play was to transport villagers to establish a base at Zhuge Liang's wind ritual spot and rush down Sun Quan with a flood of cavalry and traction trebs.
I have to imagine the Wu and Shu versions are way easier, even though the Wu campaign is supposed to be the hardest.