Oh my did I find a good place to watch Zexal subbed!
I literally know Zexal is on Animegers. If you want to watch the subbed version with no ads and download all episodes, you really have to check out these links to the site. They also have the dubbed version but I usually watch the original Japanese with subs there. (I'm actually neutral with both the sub and the dub)
https://www.animegers.com/watch/yu-gi-oh-zexal-episode-1
https://www.animegers.com/watch/yu-gi-oh-zexal-second-episode-1



















