Not going to make any difference in generated code for any competently written compiler.
At least when I've done it, I did it because it seemed like a relatively minor activity, and I didn't want it to distract from the rest of the code.
Some mind find one bit of trivia interesting though. In PL/I you could also write code like:
A = B = 0;
Some might find the result of this a bit surprising though. PL/I didn't require use of (for example)
= for assignment and
== for comparison. Instead, it sort of...guessed what you meant by any particular use of
=. So, if you had something like
if a = b, it treated that as a comparison, but if you had
a = b; it treated that as an assignment.
In the case of
A = B = 0; things got just a little strange though: it treated the first
= as an assignment, but the second as a comparison. So, it would compare B to 0, and (like C) produce 0 for false, and 1 for true. Then it would assign that integer-representing-Boolean to A. As a result, after executing
A = B = 0; we could be certain of one thing: A would not equal B. If B was 0, then A would be 1, and if B was not equal to 0, then A would be 0.
You could, however, override its guess, so
A := B := 0; assigned 0 to both A and B.