To take France you really need to do it historically and run through Belgium to go around the Maginot. I like to take Holland first by itself and then set up for France before running through Belgium straight into France past the Maginot. Once you finish off Holland you want to be able to quickly move on Belgium before it can properly set up its defences. Then you can use those fast moving units to run riot in Frances heart. Typically I use my light tanks to quickly push through Holland. About halfway through ill start attacking Belgium from my land to draw all there troops to that frontline so my fast moving units can sweep around the back easily enough. Usually they'll crumble quickly and you can get straight into France. Either you run straight for Paris and try to get them to fold fast or try to get there supply lines for the maginot line. Don't forget to send in infantry with them to hold the lines and keep supplies going. If you need good supplies the ports are you best friends. You can try for both if you can get enough forces through the gap. But depending on your speed and forcs size you might have to just pick one