I definitely would not keep 24 tank divisions in one province for a couple reasons. For starters, you’ll want to attack from multiple directions at once, just for combat width reasons alone. 24 divisions won’t be able to fight all at once, but if you attack from multiple provinces you’ll increase your combat width so more tanks can bring their guns to bear.
The second is I would worry about supply consumption. Tanks tend to be pretty supply heavy so I would worry my logistics wouldn’t be able to keep up with that many tanks in one spot. A lot of that depends on what exactly your tank division is comprised of, though. From your screenshot it doesn’t look like they’re running into supply issues right now (although you have a critical supply shortage up in Scandinavia somewhere!).