app-odoo/app_account_ztree/views/account_account_views.xml

<odoo>
    <data>
    <!-- hr -->
        <record id="app_view_account_form" model="ir.ui.view">
            <field name="name">app.account.account.form</field>
            <field name="model">account.account</field>
            <field name="inherit_id" ref="account.view_account_form"/>
            <field name="arch" type="xml">
                <xpath expr="//field[@name='parent_id']" position="attributes">
                    <attribute name="widget">ztree_select</attribute>
                </xpath>
            </field>
        </record>
    </data>
</odoo>