Equating 5^2-4^2+5-4^2 to 5²-4²+5-4², I get 5²-(4²+5)=4, but I can’t find a grouping to include the final 4² and still get 4 as the result.
These don’t work either: 5²-(4²+5-4²)=20; 5²-4²+(5-4)²=10; 5²-(4²+(5-4)²)=8; 5²-(4²⁺⁵⁻⁴)²=-4071; ...
Sorry, I don’t think it’s possible.