Which interpretation best fits “مَا زَيْدٌ كَاتِبًا بَلْ شَاعِرٌ” in context?

Qasr by Coordination, Negation–Exception, and Innamā

• Context and the implicit domain — I struck no one except Zayd.
• Scholarly analyses of innamā — Only; indeed no more than.
• Restriction using bal — Zayd is not a writer but a poet.
• Word order after innamā — Zayd is only a writer.