select1

SELECT 
    row_identifier,
    RTRIM(XMLAGG(XMLELEMENT(E, chunk_content).EXTRACT('/text()') ORDER BY chunk_num).GETCLOBVAL()) as full_text
FROM (
    SELECT
        t.ROWID as row_identifier,
        c.chunk_num,
        blob_to_text_range(t.CONTRAGRP, c.start_byte, c.end_byte) as chunk_content
    FROM
        ZExecDetail t
    CROSS JOIN LATERAL (
        SELECT
            level as chunk_num,
            (level * 4000 - 3999) as start_byte,
            (level * 4000) as end_byte
        FROM dual
        CONNECT BY level <= CEIL(blob_length(t.CONTRAGRP) / 4000)
    ) c
    WHERE
        t.INTERNTIMESTAMP = to_orating_from_syb('May 25 2012 12:50:13:406PM') 
        AND t.ORDERID = '1214650eat6'
    ORDER BY t.ROWID, c.chunk_num
)
WHERE chunk_content IS NOT NULL
GROUP BY row_identifier