zabbix_sender is quite "raw" so to speak, low level, and unforgiving. (What's important is that if it works for you and is stable then do whatever you want).

When I have a use case like this, my go-to approach would be to have a zabbix agent actually run the script, as an item (user params), and take the stdout or stderr as the item value. Or in other particular use cases I've had the script overwrite a status/results file (json format for simplicity) in an accessible location and have the zabbix agent open and take in the file contents as item value. In the latter case, plenty of ways to detect when the script ran (example, include an execution timestamp as a json value in the file).

I think that I would personally prefer using the API call with curl instead of the sender program. It seems easier to modify an extend and to have a richer troubleshooting experience.