(Fatwa: 2517/2071=H /1429)
It is mustahab (desirable) to recite Tasbihat-e-Fatima after every obligatory salah, while performing Sunnah Muakkadah is nearer to essential. Obviously, sunnah is more important than mustahab. In obligatory salah after which there are Sunnat Muakkadah such as Zuhar, Maghrib, Isha, one should perform the sunnah just after the obligatory salah, and then should recite Tasbihat-e-Faitma. This is preferably better.
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband