Taking it should be within the Travelers' power. Holding it would not be - Diabolin retaliation might be delayed by as much as a day or two, but if their ground forces had trouble retaking it they'd pull back and use radioactive artillery bombardment. Their best chance is to take the factory, loot it, wreck it, and scatter.

If they push into the city as quickly as they can, they might be able to make it all the way to the local palace, but they'd take absolutely brutal losses on the way, as attacks on the Palace are something the Diabolin expect and prepare for.