While troubleshooting a Zabbix communication problem I realized that there was no Zabbix protocol dissector in Wireshark. Long story short: I wrote my own dissector in Lua as an exercise. Actually, I wrote two dissectors, one for Zabbix passive agent communication (port 10050, the not-so-json-style protocol) and one for other Zabbix components (port 10051).
You can find the dissectors in GitHub: markkuleinio/wireshark-zabbix-dissectors
See also my earlier post about Zabbix components and ports.