What is nowadays called silazane?
It seems this name should not be in the blue book. It is an error.

The following instruction is what Corrections to Nomenclature of Organic Chemistry. IUPAC Recommendations and Preferred Names 2013 has given for your problem:


  Page 82, P-15.3.2.4.1, example 4 on this page.
  Delete 1,1′-(2-ethenyl-1,2,3-trimethyldisilazane-1,3-diyl)bis(ethan-1-one).


As Igors Mihailovs (OP) pointed out in comment section to the question, the Recommendations 2013 are not error-free. You may see how nany errors have been corrected in this web page. For example, page 75 has 4 errors in that page alone!