如果我没有理解错的话，这就是您现在所拥有的（尽管进行了一些简化，以便避免（不必要的）数据类型转换）：

SQL> with
  2  mp (creation_date) as
  3    (select to_date('2022-11-19 10:17:32', 'yyyy-mm-dd hh24:mi:ss') from dual),
  4  wl (timezone_code) as
  5    (select 'Europe/Zagreb' from dual)
  6  select to_char(cast(creation_date as timestamp) at time zone wl.timezone_code,
  7                 'yyyy-mm-dd"T"hh24:mi:ss.ff3TZH:TZM') result
  8  from mp cross join wl;

RESULT
-----------------------------
2022-11-19T10:17:32.000+01:00

如果您建立接受日期值和时区代码的函数：

SQL> create or replace function to_iso8601
  2    (par_value in date, par_time_zone in varchar2)
  3  return varchar2
  4  is
  5  begin
  6    return to_char(cast(par_value as timestamp) at time zone par_time_zone,
  7                 'yyyy-mm-dd"T"hh24:mi:ss.ff3TZH:TZM');
  8  end;
  9  /

Function created.

然后将其用作

SQL> with
  2  mp (creation_date) as
  3    (select to_date('2022-11-19 10:17:32', 'yyyy-mm-dd hh24:mi:ss') from dual),
  4  wl (timezone_code) as
  5    (select 'Europe/Zagreb' from dual)
  6  select to_iso8601(mp.creation_date, wl.timezone_code) as creation_date
  7  from mp cross join wl;

CREATION_DATE
--------------------------------------------------------------------------------
2022-11-19T10:17:32.000+01:00

SQL>

如果你有一个只读访问权限，那么你将不能创建一个函数。但是，CTE（正如你提到的）来拯救！

SQL> with
  2  function to_iso8601
  3    (par_value in date, par_time_zone in varchar2)
  4    return varchar2
  5    is
  6    begin
  7      return to_char(cast(par_value as timestamp) at time zone par_time_zone,
  8                   'yyyy-mm-dd"T"hh24:mi:ss.ff3TZH:TZM');
  9    end;
 10  --
 11  mp (creation_date) as
 12    (select to_date('2022-11-19 10:17:32', 'yyyy-mm-dd hh24:mi:ss') from dual),
 13  wl (timezone_code) as
 14    (select 'Europe/Zagreb' from dual)
 15  select to_iso8601(mp.creation_date, wl.timezone_code) result
 16  from mp cross join wl;
 17  /

RESULT
--------------------------------------------------------------------------------
2022-11-19T10:17:32.000+01:00

SQL>