Maybe I am missing something, but Zikr sounds suspiciously like japa (https://en.wikipedia.org/wiki/Japa), which is a well accepted form of concentration meditation in all Dharmic traditions. Many teachers will ask neophytes to have a regular japa practice, where you recite a mantra a certain number of times often with the help of a mAlA, first audibly, and gradually, mentally (https://en.wikipedia.org/wiki/Japa#Degrees_of_loudness). The idea being that it's easier to focus on a gross object at first to keep your mind steady, and later proceed to more subtle forms. Patanjali himself recommends that Om be chanted and its meaning reflected upon (https://www.himalayanacademy.com/saivite-scriptures/patanjal...).

The forms of meditations in dharmic traditions is quite bewildering. Patanjali himself recommends to concentrate on anything that you are comfortable with (https://www.himalayanacademy.com/saivite-scriptures/patanjal...).

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.