Q: When should one read the after Salaah Adhkaar (Zikrs): after the Fardh or the Sunnan ?
A: The Sunnah Salaah is linked to the Fardh Salaah in the sense that it has been prescribed to make up for deficiencies in the Fardh Salaah and complete it. Therefore, it should be performed immediately, without delay.
Keeping the above in mind, it is preferable to read the post-Salaah Adhkaar, only after having perrformed the Sunnan Salaah .However, there will be no problem with reading it immediately after the Fardh Salaah. (Raddul Muhtar 1:530)