xml schema putting both sequence and all under one complexType node

Question

Here is the xml file:

<section>
    <number>1</number>
    <title>A Title goes here...</title>
    <code>TheCode</code>

    <element></element>
    <element></element>
</section>

In section node, there are number, title and code node. Their sequence must not be fixed. Then, there are multiple element under section node as well.

The idea is to use the following schema:

<xs:complexType name="Type-section">

  <xs:all>
    <xs:element name="number" minOccurs="0"></xs:element>
    <xs:element name="code"  minOccurs="1"></xs:element>
    <xs:element name="title"  minOccurs="1"></xs:element>
  </xs:all>

  <xs:sequence>
    <xs:element maxOccurs="unbounded" name="element"></xs:element>
  </xs:sequence>
</xs:complexType>

But it is invalid. I just cant put "sequence" and "all" together in the same level. How can i fix it?