Let's estimate that it will take somewhere between ~15-20(?) turns to eliminate Qin. At that point, we want to attack Tokugawa immediately in the south. If we do not attack, our stack is stuck in limbo.
Tokugawa is needed to access Churchill, either as a matter of necessity (Ice) or as a matter of speed (Galleons are slower). In ~15-20 turns, we need to have transported enough troops
to wipe out Churchill entirely. Let us assume that whatever troops attack Churchill will be unable to return (again, as a matter of necessity or of speed).
The number one priority is to establish a beach-head in England. We need to assemble a stack of ~10 units to take Warwick ASAP. We can then push on or ask for a ceasefire, depending on how the war proceeds. In these few turns, we can use Workers to scout Peter as best as we can.
After Warwick is captured, Peter will temporarily become our number one priority. He isn't dangerous, but he can research Engineering. This would be a huge time sink, so let's do as much damage as we can before then, all the while remembering that
the turn we conquer Qin is the turn (or turn before) we should DOW against Tokugawa. To repeat, at this point we need to have moved all the necessary troops to wipe out Churchill.
---
While warring against Tokugawa, the southern stack is limited to moving one tile at a time for 9 turns, simply in order to reach Kyoto:
After the ~9th turn is done, we need to have troops in place to rush Tokugawa from the north:
The southern stack's movement will determine our overall victory date. The sooner this invades, the sooner it can proceed from Tianjin ---> Tokyo ---> Kyoto. The north is much more flexible. We can control the flow and direction of all our new troops, emphasizing Peter or Toku as applicable.
Finally, after Kyoto is captured, Toku's remaining cities will all lose the 25% Chichen Itza boost (= 1.5 Trebs per city). I assume that we will be attacking with siege units more freely at this point, simply to shave a turn or two off our victory date. Taking this bonus away from all his recent Jungle cities will definitely help.