Use one pan for "difficult" vegetables, such as those that bleed (radishes) or aromatic cruciferous vegetables (radishes again and turnips). Use the other pan for the more neutral potatoes, carrots, squash, and celery. Start with the longest-cooking vegetables, such as potatoes and carrots, then add the quicker-cooking ones, such as zucchini, as you go along. Don't worry about each vegetable being utterly perfect. You can always remove them individually as they finish cooking.