From my experience, there are a handful of
Insurance companies that will make your claim go through easily, but you have to pay more for that sort of service. Hope I am not tempting fate here, but having had only one windscreen claim in the last 12 years, I tend to look at the cheapest quotes.
I have been with AXA/Swiftcover for a few years now. With my windscreen claim last year, I spoke to Paul at Glasstec Automotive (highly recommended for our cars btw), and AXA were only willing to put an aftermarket screen using Autoglass. With a few words of advice from Paul, I managed to get AXA to agree to put a genuine Porsche screen using Glasstec. I had to give them a quote, and Glasstec were cheaper by £300 with a Porsche screen compared with Autoglass with a non-genuine screen! Believe it or not, Porsche Bournemouth were even slightly cheaper than Glasstec.
All these
Insurance companies will do their best to get you to comply with their terms and conditions, and that is what you sign upto in their small print (which most people do not read). When I was with another discount insurer years ago, I had a claim, they were trying to get me to used an approved repairer, and if not get two quotes etc. When I spoke to the garage I wanted to use, they advised me on what to say, and with a few key words: "dangerous, unsafe to drive", the insurer were left with no option but to have my car picked up and taken to the garage I chose.
I can see Zenith, being the cheapest on my search results by far, probably likely to be even more "sticky" with their rules, and even more difficult to deal with, so it will be sensible to just not take the chance and avoid.