well after more than 6 weeks later, I finally received a response from Edelweiss, unfortuantely, not the answer I was looking for - see below. Any suggestions to challenge this or should I let it go? seems very frustrating after such a long delay!
We are pleased that you considered Edelweiss when planning your trip to Croatia. All the more we regret that you were affected by the delay of the flight from Split to Zurich on the 1st of August 2018.
It is true that flight WK449 on 1 August 2018 could not take place according to schedule. Due to a thunderstorm, the aircraft was struck by lightning and therefore the necessary repairs took some time interrupting the flight rotation.
As the airport in Zurich does not allow landings during the night and in the meantime our crew for the return flight had reported for duty as scheduled, meaning that the maximum number of permissible working hours for the crew would have been exceeded. The stopover in Milan was necessary as per international aviation safety standards.
This unusual and unforeseen sequence of events could not be planned for in advance. Nevertheless Edelweiss prioritised the safety of both our passengers and our crew, while also doing everything possible to operate the flight while minimising still further delays.
We understand that the delay has affected not only our timetable but, above all, your travel plans. Nevertheless, we point out that the law applicable in some EU Member States according to the ECJ ruling of 19 November 2009, according to which compensatory payments are due in the event of a delay in arrival, does not apply in Switzerland.