The opening du'a, if you do not move your lips.

Allah the Mighty and Majestic says, as in the sacred narration: I am with My servant as long as he remembers Me or his lips move with Me. That is why we say that moving the lips is required, and this has also been mentioned.

From Abdullah ibn Mas'ud, may Allah be pleased with him, regarding the condition of moving the lips.

So we also see that a person hears himself, so based on this we say that it is necessary to move the lips, even if we say that a person reads in his heart without moving his lips.

Then it would be permissible to say Al-Fatiha and also the rest of the adhkar, remaining silent, and we would say what is in the heart is contemplation.

But as for the tongue and the lips, that is dhikr.

There is a difference between dhikr and remembrance, even if it falls under the categories of reflection.

When it comes to a person's reflection or what falls under the categories of dhikr, a person remembers what he forgot.

What he forgot in general terms, but in terms of the Islamic definition, we say dhikr is what the lips move with, and as for reflection, it is what is in the heart and the mind. And Allah knows best.