I want to populate filtered value from one doctype to another

ERPNext
1

I want to filter the Employees to Sales Order where the employees Designation is “Zonal manager”

How can i filter the employees ?

The Customer have custom field called Zonal Managers i want to populate values in there


frappe.ui.form.on('Customer', {
    onload: function(frm) {
        // Fetch and populate Zonal Managers when the form is loaded
        fetchAndPopulateZonalManagers(frm);
    }
});

function fetchAndPopulateZonalManagers(frm) {
    // Query Employees with designation 'Zonal Manager'
    frappe.call({
        method: 'frappe.client.get_list',
        args: {
            doctype: 'Employee',
            filters: {
                designation: 'Zonal Manager'
            },
            fields: ['employee', 'employee_name']
        },
        callback: function(response) {
            if (response.message && response.message.length > 0) {
                // If Zonal Managers found, populate the field
                let zonalManagers = response.message;
                let zonalManagerOptions = [];
                zonalManagers.forEach(function(manager) {
                    zonalManagerOptions.push({
                        'label': manager.employee_name,
                        'value': manager.employee
                    });
                });
                // Set options for Zonal Manager field
                frm.set_df_property('custom_zonal_managers', 'options', zonalManagerOptions);
                frm.refresh_field('custom_zonal_managers');
            } else {
                // No Zonal Managers found, show a message
                frappe.msgprint(__('No Zonal Managers found.'));
            }
        }
    });
}

This code is not working can any one help