Learn Spanish (Spain): El impacto es obvio y de ello deducimos la hipótesis. - The impact is obvious and from it we deduce the hypothesis.

In this sentence, ello does not just replace the noun el impacto. It refers to the entire preceding idea: the fact that the impact is obvious. We use the neuter pronoun ello to refer back to abstract concepts, statements, or whole situations rather than specific masculine or feminine nouns.

Could I use eso instead of ello in this sentence?

Yes, and in fact, de eso is much more common in everyday spoken Spanish. The pronoun ello is quite formal and is mostly used in written texts, formal speeches, or fixed expressions.

Why can't we use the direct object pronoun lo here, as in de lo deducimos?

The word lo cannot be used right after a preposition. When a neuter pronoun is the object of a preposition like de, you must use a prepositional pronoun like ello (or eso, esto, aquello). The pronoun lo is strictly used as a direct object that goes with a verb.

Since deducir ends in -ir, is deducimos in the present or the past tense?