Whats the total supply of zoi?
21 millions. It would be around 12 millions after the first 6 months.
This is not true, this coins source is based on XZC's source where a big error in the code allowed "hackers" to create an arbitrary number of coins for themselves using malicious zerospend transactions.
https://zcoin.io/zcoins-zerocoin-bug-explained-in-detail/You can't really tell how much coins where maliciously generated, until you do some investigations with the block explorer but probably a lot

I don't read code but the exploit has since been fixed on 28th March release right?
At time of bug, ZOIN was 'dead' with a CAP of <$1000 so it's less likely it was exploited than Zcoin & Zcoin now has a valuation of $15 million despite that.