Here's how I did it:
Firstly, Ignore Spain/Portugal. Don't deploy any armies there, but don't move any away from there either or England will attack. Sometimes England attacks anyway in turn 1 (if they do I would just restart immediately).
Turn 1 is the most important. If you get unlucky, you might want to restart before continuing to second turn. In doing first turn deployments, reinforce every border up to 9 units except for Norway, which you can keep at 6 or 7. You should have 2 or 3 units left over, put them somewhere on your eastern border.
On turn 1, move your armies from France towards your borders. Make sure to move the armies first so you get the defender advantage when the AI attacks. The AI will probably break your Rhine or Italy bonus, so long as you get the 8 army bonus from France though its ok.
Be sure to break the Austria bonus on turn 1. The minimum army income is 0 so once their bonus is broken, they get no more armies for the rest of the game unless you let them have their bonus back. You can ignore that AI once they exhaust their units trying to attack you. You'll pick up the Austria bonus later.
Austria needs to attack your Italy territory or the Rhine territory. If they attack to the North (along with Prussia), you may as well restart as the France bonus is being broken next turn and there isn't really anything you can do about it.
Make sure to have Denmark and Norway attack Sweden. These should be your final attacks/moves of the turn to ensure that you capture Sweden (Sweden will only have 1 unit left after using all its units attacking Denmark or Norway). If you don't get Sweden because you were able to successfully defend on Denmark or Norway, that's fine. The important thing is that you want to keep Russia out of the game for as long as possible because they have the highest income.
On to turn 2: You'll probably want to put some more armies on the border with England so they can't break the France bonus. Based on what happened in turn 1, place your armies down, make your army moves and then break the Prussia bonus to reduce another AI income to 0. I think I only broke the Prussia bonus on turn 3 - defending is more important than attacking. If you have the units available, reclaim whatever territory the Austria AI took from you on turn 1 to get that bonus back.
Make sure England doesn't break your France bonus. Sometimes you get unlucky and all the AI attack the same territory of yours to break the bonus, forcing a restart. It is important to keep Russia at bay by not letting them ever take Denmark or they get too many armies for you to defend against.
From there on out it's pretty smooth sailing. Don't eliminate the Prussia or Austria AI too early, they have income of 0 and Russia won't give them their units because they are next to large neutrals (AI is weird like that). Once those two AI have income of 0 and can't do anything once their stack is taken care of, focus on braking into England and then conquering Spain while keeping Russia away. By this point England would likely have attacked one of your France territories, so long as they don't conquer it you're fine (and if they do get it, if you get into England on the same turn you might still be fine, I never had that situation happen - just make sure you recapture it ASAP and don't let Russia in and you should be fine). Make sure Denmark always has enough units to defend against Russia's attacks, if you were able to conquer Sweden on the first turn you have a couple more turns before Russia is in the game, based on how turn 1 went you might even be lucky enough that you can attack Finland to further stall and distract Russia.
Once you have reduced the England AI's income to 0, you can then clean up the rest of the territory and pick up the other bonuses. Be careful with Spain/Portugal, make sure you always attack there last so England can't hit you on a counterattack and pick up your territory. Move into Russia through Scandinavia and break their bonus, once the Russia AI bonus is broken just clean up everything.
I broke the Russia bonus before taking care of Spain in order to win in 12 turns. It is hard and definitely has a fair bit of AI luck involved but is definitely possible.
Here's a screenshot of my typical starting army layout. Sometimes the 11 would be on the top right Italy territory. https://cdn.discordapp.com/attachments/342411440197599232/735297716757725338/Screen_Shot_2020-07-21_at_8.49.50_PM.png