How to check if both are not equal in if statement?

I have so many of these in my code:

if ( x1 == x2 && y1 == y2) {
    // do nothing
}
else {
    // do the thing
}

I wonder if I can replace it with just if, without else, to make the code cleaner. I tried the following:

if ( x1 != x2 && y1 != y2) {
    // do the thing
}

but it doesn't work because if only one of them is not equal, then the whole thing is false.