I have to say it's really cute and it's a good idea to let Zails look or maybe even be older then Tails because they are counterparts and it fits them well. I even think that Zails is, because of his age, smarter then Tails and that would be totally awesome! I hope he will appear soon in the FanFiction I'm reading. It's called "Caring for your Rival" (I think so. I read it along time ago. I have to check it up..) It's mostly about Sonic and Shadow, but Zonic and Zhadow and some other Zone Cops are involved too!