Answered by Shaykh Faraz Rabbani
Question : Can the Imam lead dhikrs after the Salah?
The sunna is to recite the post-salah adhkar , and it genrally understood to recite them silently. However, if there is an interest in the imam or anyone else raising his voice to remind others to say them (such as by raising their voice for the first instance of each set of dhikrs), then there is no harm in this, as long as it is not deemed to be a specific religious obligation. [Abu Sa`id al-Khadimi, Rasa’il wa Fatawa].
However, one is not bound to follow them, if reciting more slowly is more conducive to one’s concentration or presence of heart. In such cases, do so with discretion.
And Allah alone gives success.