Zikr is “remembrance of God”. Typical “mantras” are specific names of God, as given by the Pir (elder) to the seeker/neophyte.

https://en.wikipedia.org/wiki/Dhikr

So of course, Zikr is a subset of general contemplation and given the universality of human body and psyche, you will find shared elements (such as seating, lowering & raising of head/gaze, and the big one, breathing) in various methodologies of contemplation across cultures, religions, and schools. This is to be expected and is natural.

In a sense, one could possibly say that Meditation aimed towards mastering the mind, whereas Zikr aims for breaking the imaginal boundary of lower self (i.e. aims for Unity of Selves harmonized by “Names”) by being fully focused and mindful of ‘The One’. Chanting Om is quite close to the effect.