DraStic

You can't. You can only have one set or the other, not both at the same time.

That said, someone made a ROMhack that does what you need, and doesn't even need the Zero 3/4 ROMs or save files! It'll probably be easier to patch the game on a computer, but you might be able to do it on your phone if ...

I'm having a save issue with Meteos, in that it refuses to accept an old .dsv from my computer and says it has to reformat the save data to continue. The save works fine in Desmume and even if I copy the save from the cart through TWLSaveTool on a hacked 3DS and import it into Desmume, it works ...