app-odoo/app_product_ztree/views/product_views.xml

<odoo>
    <data>
        <!-- Product -->
        <record id="app_product_template_form_view" model="ir.ui.view">
            <field name="name">app.product.template.form</field>
            <field name="model">product.template</field>
            <field name="inherit_id" ref="product.product_template_form_view"/>
            <field name="arch" type="xml">
                <xpath expr="//field[@name='categ_id']" position="attributes">
                    <!-- Add your fields or attributes here -->
                    <attribute name="widget">ztree_select</attribute>
                    <attribute name="options">{'ztree_parent_key': 'parent_id','ztree_expend_level': '1', 'ztree_name_field': 'name', 'order': 'name' }</attribute>
                </xpath>
            </field>
        </record>
        <record id="app_product_category_form_view" model="ir.ui.view">
            <field name="name">app.product.category.form</field>
            <field name="model">product.category</field>
            <field name="inherit_id" ref="product.product_category_form_view"/>
            <field name="arch" type="xml">
                <xpath expr="//field[@name='parent_id']" position="attributes">
                    <!-- Add your fields or attributes here -->
                    <attribute name="widget">ztree_select</attribute>
                    <attribute name="options">{'ztree_parent_key': 'parent_id','ztree_expend_level': '1', 'order': 'name' }</attribute>
                </xpath>

            </field>
        </record>
    </data>
</odoo>