Accessing structure descendants data
You would loop through the Matrix field within each tab the same way you’d do it for any other element.

{% set tabs = entry.descendants %}
{% for tab in tabs %}
    {{ tab.title }}
    {% for block in tab.myMatrixFieldHandle %}
        {% if block.type == 'about' %}
            ...
        {% elseif block.type == 'team' %}
            ...
        {% elseif block.type == 'clients' %}
            ...
        {% endif %}
    {% endfor %}
{% endfor %}