يَعْلَمُونَ مَا تَفْعَلُونَ
Sentence structure
The verbal clause further describes the guardians. يَعْلَمُونَ takes relative مَا as its object; تَفْعَلُونَ is its relative clause, with the returning object pronoun omitted.
Ayah summary
They know your deeds; none remains hidden from them or unrecorded.
يَعْلَمُونَ — They know
Grammar: A third-person masculine plural imperfect of the five verbs. Attached و is the subject and final ن marks the indicative; the clause describes the guardians.
مَا — whatever
Grammar: A relative pronoun functioning as the object of يَعْلَمُونَ.
تَفْعَلُونَ — you do
Grammar: A second-person masculine plural imperfect of the five verbs. Attached و is the subject and final ن marks the indicative; the clause is the relative clause of مَا. Its returning object pronoun is omitted.