how would you speed up this long query?

select
      sub_query_1.pid,
      sub_query_1.tit,
      sub_query_1.num,
      sub_query_3.cid,
      sub_query_3.id,
      sub_query_3.c,
      sub_query_3.s,
      sub_query_3.z,
      sub_query_3.cy,
      sub_query_3.cd,
      sub_query_3.cr,
      org.id as org__id,
      org.pid as org__pid,
      org.open,
      org.cid as org__cid,
      z0.zcg
from
      (select
                  proj.pid,
                  proj.tit,
                  proj.num
      from
                  proj,
                  (select
                              org.pid
                  from
                              org
                  where
                              org.open = 'Y') as sub_1
      where
                  proj.pid = sub_1.pid) as sub_query_1,
      (select
                  detail.cid,
                  detail.id,
                  detail.c,
                  detail.s,
                  detail.z,
                  detail.cy,
                  detail.cd,
                  detail.cr
      from
                  detail,
                  (select
                              org.id
                  from
                              org
                  where
                              org.open = 'Y') as sub_3
      where
                  detail.id = sub_3.id) as sub_query_3,
      org,
      z0
where
      sub_query_1.pid = org.pid and
      sub_query_3.id = org.id and
      sub_query_3.z = z0.zcg
group by
      z0.zcg,
      sub_query_1.pid,
      sub_query_1.tit,
      sub_query_1.num,
      sub_query_3.cid,
      sub_query_3.id,
      sub_query_3.c,
      sub_query_3.s,
      sub_query_3.z,
      sub_query_3.cy,
      sub_query_3.cd,
      sub_query_3.cr,
      org.id,
      org.pid,
      org.open,
      org.cid