rezultato

Look at this word with an Esperantist's eye and it reads as a participle: rezult- plus -at- plus -o, the thing being resulted. It is nothing of the kind. -At here is a fossil, the last two letters of the French résultat, borrowed along with the rest of the word before anyone thought about how it would parse. Esperanto is full of these quiet Latin tails - the language took international vocabulary as it found it, and only its own affixes carry meaning.

So we have two words for one idea. Rezulto is the everyday one and the one to reach for by default: the result, the outcome, the consequence, of anything at all. Rezultato survives beside it and is heard most where the result is a figure you could write down - a score, a total, a measurement, the number at the bottom of a page. That is a tendency, not a rule; you will meet plenty of writers who use them interchangeably, and neither is wrong.

The practical advice is short. Write rezulto. Recognise rezultato. And when you see it, do not go looking for a verb rezultati, because the participle you think you can see is not there.