As a start, isolate the last digit and would it help to sort the rest of the digits? BC in your problem 421 and 241 have the same solution, so you can reduce the problem set at the very least

Not all the operators are commutative, so it totally works if you consider only +, - and *, but /, ^ and % are not communitive. 3/4 != 4/3, 3^4 != 4^3 and 3 % 4 != 4 % 3, so sorting only gets you so far.