Complex sentence: Dalziel delivered her resignation letter on 17 September and delivered her valedictory speech the following day with her resignation taking effect on Friday, 11 October; the day before the local body election so that the by-election campaign did not interfere with the local body election.
Split into simpler sentences: Dalziel delivered her resignation letter on 17 September and will deliver her valedictory speech the following day. Her resignation will take effect on Friday, 11 October, which is the day before the local body election.