Remember that assignment is done right to left, and that they are normal expressions. So from the compilers perspective the line
sample1 = sample2 = 0;
is the same as
sample1 = (sample2 = 0);
which is the same as
sample2 = 0;
sample1 = sample2;
That is, sample2 is assigned zero, then sample1 is assigned the value of sample2. In practice the same as assigning both to zero as you guessed.