question to examples of rule 6.12.2

[Manni]

Hi

In Rule 12.2

nested assignment statements
Assignments nested within expressions cause additional side effects. The best way to avoid any chance of this leading to a dependence on order of evaluation is to not embed assignments within expressions.

For example, the following is not recommended:
x = y = y = z / 3 ;
x = y = y++;

I don't understand, what could go wrong here:
1. x = y = y = z / 3 ;
2. x = y = y++;

If x = 1, y = 2, z = 3, I would say,

- for 1. the result for x is everytime 1
- for 2. the result for x is everytime 3

What could a compiler make different here?

thanks