Prova detta:
with t(d) as (
select '<efwewfsdf/>
<asdf>
<qwe>
<rej:aaa ns2=rnsjvnsvjrlntjnbsnbltdbk">64-0203-0875/4</rej:aaa>
<rej:bbb ns2=bmtbrbpnrtusrnbdbd k">06396</rej:bbb>
<rej:ccc ns2=vmkfbkmbkfmgkmfgkbgfk">4567650</rej:ccc>
<rej:ddd ns2=zxczxczczxczxczxk">402341198</rej:ddd>
<rej:eee ns2=asdasdasdazxck">723112</rej:eee>
<rej:eee ns2=adasdasdawawqweqwek">342253</rej:eee>
<rej:eee ns2=bgbgfnnhnhnhnhnhnk">656345</rej:eee>
<rej:fff ns2=ewretyrtyghnk">352</rej:fff>
<rej:ggg ns2="vzxczdvdbdfgs">asd.Gdsa</rej:ggg>
<rej:hhh ns2="zcsasdqwfwgerbyn">W1_22</rej:hhh>
</qwe>
</asdf>' from dual
), t1(d) as (
select SUBSTR(d, REGEXP_INSTR(d, '<[A-Za-z]{3}:', 1, level), REGEXP_INSTR(d, '</rej:[A-Za-z]{3}>', 1, level) - REGEXP_INSTR(d, '<[A-Za-z]{3}:', 1, level))
from t
connect by rownum < LENGTH(d) - LENGTH(REGEXP_REPLACE(d, ':[A-Za-z]{3}>', ''))
)
select REGEXP_REPLACE(d, '^<rej:.*">', '') ff from t1
FF
--------------
64-0203-0875/4
06396
4567650
402341198
723112
342253
656345
352
asd.Gdsa
W1_22