Are the three recitations of Al-Mu'awwidhatayn and Surat Al-Ikhlas after the Fajr and Maghrib prayers sufficient to replace their re-recitation for the morning and evening remembrances?

It is from the Sunnah (definition) to recite Surat Al-Ikhlas (definition) and the two Mu'awwidhat (Surat Al-Falaq and Surat An-Nas) three times in the morning and in the evening, and once after the obligatory prayers. The principle is that the recitation for the morning and evening remembrances and the recitation after the prayer are independent, and a single recitation does not suffice for both of them.