إِنْ قُصِدَ تَشْرِيكُ الثَّانِيَةِ لَهَا فِي حُكْمِهِ
If the second clause is meant to share the first clause’s grammatical function.
Where the first clause has a syntactic position, the reason for coordination can be to place the second clause in precisely that function. “Zayd writes and composes poetry” groups both verbal predicates under the same subject.
This is coordination to share a grammatical status, not merely a pleasant rhythm or a loose association of two facts. Their identical external function matters even if each clause retains its independent internal structure.