The 'secret' to defeating the French quickly is Armour. Disband all your bombers on the first turn. They are very useful units to be sure, but not as useful as the Panzers you will buy with them.
Buy three panzer corps first turn. Then buy one a turn (disbanding infantry) until they will no longer show up as a reinforcement by May 1st. Then do the same buying Mech...one per turn.
Keep the fighters. For May 1st I end up with 6 Panzer corps and 2 mech corps, with 6 Fighters. Along with another Panzer and Mech entered as reinforcement...
You will have disbanded about a dozen or so infantry corps...but you will have 7 panzer corps and 3 mech corps..and the French front is very tight...you won't miss them.
The lack of bombers will also mean the lack of air attrition...the allied fighters can't shoot down something that doesnt exist.
The next turn you will punch a large hole in the french lines and take Lille. If the english are in France, you can play conservatively and kill them. If they are not, you will be adjacent to Paris. Third turn you take Paris if no English..otherwise you continue to kill them.
Having breakthrough panzers with 10 attacks is huge. Once a unit is dislodged, it is no longer fortified, has suffered readiness and will die when a leap frogging panzer kills it.
The big down side (of course) is no bombers. Which means you are relying on fighters to provide for you. I found that with my 6 fighters, I was able to gain an odds on my attack on Paris.
It is June 21st and I have just installed Vichy and I am doing my turn. My friend knew what I was planning and wisely left the English out of France, so only the French suffered.

“My logisticians are a humorless lot … they know if my campaign fails, they are the first ones I will slay.” – Alexander the Great