onders.org_zola_theme/templates/shortcodes/modal.html

{% if section %}
{% set full_path = section.path ~ path %}
{% endif %}
{% if page %}
{% set full_path = page.path ~ path %}
{% endif %}
{% set thumb = resize_image(path=full_path, width=400, height=400, op="fit") %}

<div>
  <a href="#{{ path }}">
    <img class="modal-thumbnail" src="{{ thumb.url }}"/>
  </a>
  <div class="modal" id="{{ path }}">
    <a href="#" class="close">
      <span class="spacer"></span>
      <img src="{{ path }}" />
    </a>
  </div>
</div>