Documentation on user macros says that:

Zabbix resolves macros according to the following precedence:

1. host level macros (checked first)
2. macros defined for first level templates of the host (i.e., templates linked directly to the host), sorted by template ID
3. macros defined for second level templates of the host, sorted by template ID
4. macros defined for third level templates of the host, sorted by template ID, etc.
5. global macros (checked last)

The fact that templates are sorted by template ID is meaningless, because:

1. user cannot see template IDs in the frontend;
2. user has very limited control of what IDs are assigned to templates;
3. documentation does not say if they are sorted in ascending or descending order.