Under EC261 as its more than 14 days out you are not entitled to compensation. You are entitled to a full refund or rebooking within a reasonable window.

Option
1. Ask to be rebooked for Sept 4th
2. Ask to be rebooked for Sept 5th to Geneva and take the train
3. Ask to be rebooked for Sept 5th onto the SWISS flight from DUB to ZRH (unlikely as no interlining agreement, but would require to collect luggage and recheck)

Otherwise this is a travel insurance case, flight cancelled