I’m going to assume that both of these relationship fields are “Post Object” and that you are returning the Post Object. Let me know if this is incorrect.
// code on the property page
// somewhere inside "The Loop"
// get the project object on from the property post
$project = get_field('project');
$product_id = $project->ID;
// get the agent object from the project post
$agent = get_field('agent', $project_id);
$agent_id = $agent_id;
// show the title of the agent post
echo get_the_title($agent_id);