Learn Italian: Questi autori non scrivono mai prologhi o epiloghi. - These authors never write prologues or epilogues.

For nouns ending in -co and -go, the plural usually depends on where the stress falls. If the stress is on the third-to-last syllable, they typically end in -ci and -gi (like medico becoming medici). However, words ending in -logo have a special rule: if they refer to a person (like a psychologist), they end in -gi (psicologi), but if they refer to a thing, they get an h to keep the hard G sound, making -ghi. Since a prologue is a thing, it becomes prologhi.

Does epiloghi follow the exact same rule as prologhi?

Yes! Epilogo also has its stress on the third-to-last syllable (e-PI-lo-go). Just like a prologue, an epilogue is a thing, not a person, so it takes the -ghi ending to become epiloghi.

Why do we need non before the verb if we are already using mai (never)?

Italian uses a double negative structure. When negative words like mai (never), nessuno (nobody), or niente (nothing) come after the verb, you must put non before the verb. So, they never write translates directly to non scrivono mai (literally they don't write never).