SaboLonzo

A very poor hack with the Cherish Ball and how it is level twenty-nine. In the event, which is the only way to obtain the shiny Mew, you have to manually capture it so it would never be in a Cherish Ball and it also appears at level thirty, not level twenty-nine. It will still be able to be used in battles and raids, as I mentioned, though. Are you wishing to keep the Mew or are you wanting to attempt a trade back?

If you want to use the Mew for battles and raids, feel free, just do not offer it for trade here.
I appreciate your understanding and if you ever have anymore questions feel free to drop me a line. Have a wonderful rest of your evening.

Once you take on the Battle Tower, the judge function will be unlocked and you will be able to see the stats as "best" etc.

You would have to re-play through the game to secure a new Zacian, unfortunately.

See, you just traded a very sought after Pokemon for a shiny Mew that is most likely hacked. Zacian, especially with it's item, is one of the most sought after Pokemon on the market right now.

It would be difficult for me to tell, without setting it on my PKHex file though there are a few tell-tell signs. If the Pokemon is in a Cherish Ball, has all six IVs, an ideal nature etc. A hacked Mew can still be utilised in battles and raids however, we just do not want them traded for legitimate Pokemon here in the community. It's all too common for someone with PK Hex to be offering shiny legends and other post generation eight shinies requesting generation eight shinies and legendaries that they can not hack because they do not have a modified Switch.

No worries. The chances of getting a legitimate shiny Mew is extremely low due to the only instance of legitimately obtaining one is by SRing an almost 20 year old Event back on Emerald. This rule is implemented to protect users from receiving hacked Pokemon; I do apologise for the inconvenience.