execute block (
  NEW_T1_FIELD_1 T1_TYPE_1 = :NEW_T1_FIELD_1,
  NEW_T1_FIELD_2 T1_TYPE_2 = :NEW_T1_FIELD_2,
  NEW_T1_FIELD_3 T1_TYPE_3 = :NEW_T1_FIELD_3,
  ...
  NEW_T1_FIELD_N T1_TYPE_N = :NEW_T1_FIELD_N,

  OLD_T1_FIELD_1 T1_TYPE_1 = :OLD_T1_FIELD_1,
  OLD_T1_FIELD_2 T1_TYPE_2 = :OLD_T1_FIELD_2,
  OLD_T1_FIELD_3 T1_TYPE_3 = :OLD_T1_FIELD_3,
  ...
  OLD_T1_FIELD_N T1_TYPE_N = :OLD_T1_FIELD_N,

  NEW_T2_FIELD_1 T2_TYPE_1 = :NEW_T2_FIELD_1,
  NEW_T2_FIELD_2 T2_TYPE_2 = :NEW_T2_FIELD_2,
  NEW_T2_FIELD_3 T2_TYPE_3 = :NEW_T2_FIELD_3,
  ...
  NEW_T2_FIELD_N T2_TYPE_N = :NEW_T2_FIELD_N,

  OLD_T2_FIELD_1 T2_TYPE_1 = :OLD_T2_FIELD_1,
  OLD_T2_FIELD_2 T2_TYPE_2 = :OLD_T2_FIELD_2,
  OLD_T2_FIELD_3 T2_TYPE_3 = :OLD_T2_FIELD_3,
  ...
  OLD_T2_FIELD_N T2_TYPE_N = :OLD_T2_FIELD_N,
...
   T3
...
   T4 
)
as
begin

  update TAB_1
  set
    T1_FIELD_1 TYPE_1 = iif(:NEW_T1_FIELD_1 is distinct from :OLD_T1_FIELD_1, :NEW_T1_FIELD_1, T1_FIELD_1),
    T1_FIELD_2 TYPE_2 = iif(:NEW_T1_FIELD_2 is distinct from :OLD_T1_FIELD_2, :NEW_T1_FIELD_2, T1_FIELD_2),
    T1_FIELD_3 TYPE_3 = iif(:NEW_T1_FIELD_3 is distinct from :OLD_T1_FIELD_3, :NEW_T1_FIELD_3, T1_FIELD_3),
    ...
    T1_FIELD_N TYPE_N = iif(:NEW_T1_FIELD_N is distinct from :OLD_T1_FIELD_N, :NEW_T1_FIELD_N, T1_FIELD_N),
  where
    (KEY_COND);

--  if () then
--  update or insert into
--  else 
--  delete
   
  update TAB_2
  set
    T2_FIELD_1 TYPE_1 = iif(:NEW_T2_FIELD_1 is distinct from :OLD_T2_FIELD_1, :NEW_T2_FIELD_1, T2_FIELD_1),
    T2_FIELD_2 TYPE_2 = iif(:NEW_T2_FIELD_2 is distinct from :OLD_T2_FIELD_2, :NEW_T2_FIELD_2, T2_FIELD_2),
    T2_FIELD_3 TYPE_3 = iif(:NEW_T2_FIELD_3 is distinct from :OLD_T2_FIELD_3, :NEW_T2_FIELD_3, T2_FIELD_3),
    ...
    T2_FIELD_N TYPE_N = iif(:NEW_T2_FIELD_N is distinct from :OLD_T2_FIELD_N, :NEW_T2_FIELD_N, T2_FIELD_N),
  where
    (KEY_COND);
  
  update TAB_3
  ...   

  update TAB_4
  ...   

end