No, Arzel specifically told me I wasn't pronouncing his name correctly. My method was fine as I was following the instructions in NAP.
It was a lot easier after I learned how to pronounce his name correctly. So it does matter.
Arzel most likely showed up the first few times despite my mispronunciation of his name because, he knew I was new at evocation, plus I had a lot of help from spirit guides, etc. But he did make it clear I needed to learn the proper pronunciation of his name.