Prueba de esta manera:
Código PHP:
$query = mysql_query("
SELECT
(Select MAX(fecha) FROM fororesp WHERE id_post = fc.id_post),
fr.id_post,
fr.titulo,
fr.categoria,
fr.seccion,
fc.id_rpta,
fc.id_post,
UNIX_TIMESTAMP (fc.fecha) AS fechas,
fc.idautor,
fc.autor
FROM
foros fr,
fororesp fc
WHERE
fr.id_post = fc.id_post
AND fr.seccion<>'Zona X'
GROUP BY
fc.id_post
ORDER BY
fc.fecha DESC
LIMIT 0, 10
") or die(mysql_error());
Saludos!