CREATE TABLE table_66250 ("Class" TEXT, "Wheel arrangement" TEXT, "Fleet number ( s ) " TEXT, "Manufacturer" TEXT, "Serial numbers" TEXT, "Year made" TEXT, "Quantity made" TEXT, "Quantity preserved" TEXT)

What manufacturer has a wheel arrangement of 4-6-6-4, and a Class of z-7?
SELECT "Manufacturer" FROM table_66250 WHERE "Wheel arrangement" = '4-6-6-4' AND "Class" = 'z-7'
SELECT "Manufacturer" FROM "table_66250" WHERE "Class" = 'z-7' AND "Wheel arrangement" = '4-6-6-4'