All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
No doubt it is permissible to read the Quran or Thikr in one's heart without moving the tongue; the person will be rewarded for that, Allaah willing, but this is actually considered contemplation of the Quran and not reciting or Thikr. Reciting is accomplished only by the movement of the tongue and lips, as previously explained in Fataawa 86801 and 84707.
On the other hand, it is not compulsory to perform Wudhoo’ (minor ablution) or gargle before uttering Thikr (remembrance of Allaah).
Allaah Knows best.