أَمَّا زَيْدٌ فَحَاضِرٌ
As for Zayd, he is present.
Conditional, topic-setting ammā foregrounds a topic and points toward its response, often contributing focus and reinforcement. Its response commonly takes fāʾ, as in “فَحَاضِرٌ.”
Two distinct forms:
“أَمَّا ... فَـ” — the conditional/topic-setting form, with a doubled mīm.
“أَمَا” — a separate attention form without that doubling.
Their similar spelling should not lead us to treat them as a single grammatical construction.