I declared on Mao with ~30 Cuirs and bribed in Toku. Mainly so he won't be bribed against me. Not expecting much help.
I sacrifice a worker the AI can't resist and Mao moves part of his stack on flat grassland to grab him. I clean it up.
The problem: His main stack is still sitting in Shanghai and doing nothing... so I retreat and wait for it to reach me. Going past it to attack other cities seems like a bad idea, he would wipe me out and I couldn't hold a city in his mainland without reinforcements. Ragnar's territory also stops me from launching an attack in the north to maybe get the stack moving towards me.
Again he moved part of it into my territory and I killed it. But few turns later he still has this in Shanghai: 45 units. No way you punch through this with Cuirs.
So I decided to sacrifice Bjorgvin, my city, hoping his stack captures it next turn.
Aaaand he did take it, but again he didn't use all his units. I attacked and left 1 defender alive, so he would reinforce. He did that. In the course of 3-4 turns he moved his stack in parts into the city and I killed it slowly.
After having one of his stacks wiped out earlier, Toku moves new troops through my territory. I direct them to Shanghai.
In the north, I have been fighting against the Vikings, here taking his 3rd city. Now he only has one left. I expect him to break free and beg from HC to avoid interturn-peacevassal. But Ragnar doesn't break free. No city from Mao captured yet, but now I can threaten his northern cities.
However, at this point HC has 3x my score, Mao 2x my score and while score doesn't matter too much, it basically means that this war has to be a success or game over pretty much.
Trading some stuff with a friendly Toku to stay in the game.
I capture the last city from Ragnar and he is wiped out, for whatever that's worth. Silver+Whales are nice though, cities start to hurt from unhappiness.
Still some heavy defenses in Shanghai. I have a plan though...
Tech situation, at least Mao is slowed down somewhat it seems.
I waited for Toku to bombard Shanghai's defenses and suicide his stack. I protect his guys with ~25 Cuirs.
While waiting, I didn't sleep though and moved out in the north. Toku's stack should stop Mao's from leaving Shanghai.
I even dared to sneak past Shanghai in the south (estimating that Toku needs 4-5 turns to bombard Shanghai before attacking. So meanwhile I took an important city from Mao. At this point I have about 60 Cuirs.
After Toku finally attacks, the big cleanup starts.
Meanwhile Cathy makes contact. I trade with her, since the last civ should be Mansa (or Hammurabi?) I don't care about "worst enemy trade". I need stuff now.
Next I move towards Mao's capital, combining the stack from the north with veterans from the Shanghai slaughter. Was as painful as it looks.
Next I prepare for taking two big cities on the same turn...
And finally, Mao is ready to capitulate.
Tech picture looks like this. I think the age of Cuirs is over.
So what do I do with my 70 Cuirs now?
I need to tech Communism and Biology badly. Start teching again. Declaring on Toku now doesn't seem like a good idea, I don't want to know how many troops he has. And super-rifles in a few turns.
. So you would start golden age as soon as possible, not wait for peace with Raggy first?
... he had 0 gold, should I have done something?
Looks like it can be quite painful. May by cannons can be better then? On the other hand...with 20+10 start the war then wipe Ragnar as much as you can and then try tactical defencive war against Mao and his SoD? Probably it could require at leats 25 full cuirs. And also he has pikes. Anyway, I beleive you 
Should you try to go deep into his territory, capture several week defended cities and then ask for a peace? Those protective longbows are very annoying against Cuirs, especailly when AI has so many of them. So, I wish a lot of good luck for you 
And I wish you eventually win this game as several others. 
