 <ul>
            <li><kbd>CTRL</kbd> + <kbd>SHIFT</kbd> and drag out a selection to select geometry to hide. The selection area will appear green.</li>
            <li>Before releasing the left mouse button, or before lifting the stylus pen, press <kbd>ALT</kbd>. The selection area will turn red. You can then release the left mouse button or lift the stylus pen.</li>
            <li>In Tools &gt; Geometry &gt; Modify Topology, click Del Hidden.</li>
            <li>Optionally, in the same panel, you may click Close Holes to cap open holes.</li>
        </ul>
             
		<div class="ratio ratio-16x9">
			<iframe title="Delete Hidden Geometry in ZBrush" src="https://www.youtube.com/embed/wFh26P80oC4" data-allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowFullScreen></iframe>
		</div>

		<h4>Related Tips</h4>

		<ul>
			<li><strong>Show hidden geometry</strong>: Press <kbd>CTRL</kbd> + <kbd>SHIFT</kbd> and then click on empty area of the canvas.</li>
			<li><strong>Toggle between hidden/shown geometry (reverse visibility)</strong>: Press <kbd>SHIFT</kbd> + <kbd>CTRL</kbd> + Click and drag background.</li>
			<li><strong>Show only one given polygroup</strong>: Press <kbd>CTRL</kbd> + <kbd>SHIFT</kbd> and click on the given polygroup.</li>
		</ul>

Procedure for deleting hidden geometry in ZBrush and optionally capping open holes.