How to find the difference of two numbers in assembler?

Question

assembler

Hello!
Task: find Z = X - Y , where X, Y are double words (4 bytes), on a 16 -bit processor.
So far, I could only come up with such an algorithm: extract byte by byte from the end of X in AL, compare with the corresponding byte Y, if the extracted byte X is less than resp. byte Y, add +1 to register AH, subtract 1 from [Y + 1], subtract and write the result to Z. But such an algorithm, for example, will not get the correct Z if X is less than Y. And, as it seems to me, he is suboptimal.
Maybe there is some more optimal and correct algorithm? Maybe you can somehow use the flag registers?