Using potis as an adjective to describe the subject of discimus would make more sense for what you're trying to say. I think you're misinterpreting able, however. Using it as an adjective or even as an adverb implies that the people doing the learning are doing it well, or capably, which is not, imo, the intent of the OP's phrase. Opinions differ.

Potis and quom are two weird word choices. I don't know how else to say that. Potens is much more common to use as an adjective, and the verb possum is damn near ubiquitous. Potis kind of works but it's no one's first choice. Same goes for quom. Two of my dictionaries don't even have it. The one that does simply directs you to cum. Then there is Whitaker's Words, which has the same entry for quom and cum, which indicates to me it's either a really old form of cum, or one written by a monk by accident. You know how these things go. See the relative pronoun for the relationship between "qu" and "c."

Your second use of potis is for poetic effect, I assume. So, whatever. Know that it's addition implies a relationship between it an something else in that phrase. You've changed omnes to omnia, but potis could still go with that. "All things able to be understood." That sort of works. But you're using it with qui to effect parallelism with quom, and everyone's first thought at qui potis is "who is able."

And, you know, sorry to everyone reading this. And to you in particular. I clearly misjudged you. My difficulty with your translation boils down primarily to those weird word choices, which you have to admit are uncommon and so seem like something plucked from a thesaurus. You've got me on the whole passive periphrastic thing, but really an implied sunt isn't going to throw anyone off their game.