No, you cannot nest analytic functions. From the manual:
You cannot nest analytic functions by specifying any analytic function in any part of the analytic_clause. However, you can specify an analytic function in a subquery and compute another analytic function over it.
For example:
SQL> select sum(count(*) over ()) over () from dual;
select sum(count(*) over ()) over () from dual
*
ERROR at line 1:
ORA-30483: window functions are not allowed here