I think maybe the title is better than the example.
It’s not about “recalculating when zero”. It’s about “an IF() must never evaluate both the true & false results, because for example that could lead to a division by zero error from the route which the IF() will not follow. It must evaluate the condition first, and only then decide which single one of the two result to evaluate.”. But as you see fit.
BTW, I found If Formula not working in RuleJS, but that’s not the one where I suggested to someone the nested-IF workaround.