This chain is having some issues - there are a few forks out there and people who are on the wrong forks are making things worse by broadcasting bad chain data to others trying to sync.

The longest chain I have seen is fortunately the fork the exchanges are on - they are on block ~37,000 right now. If your wallet is "synced" but not on block 37000 or later, you are on a bad fork whether you like it or not. You can check what block the exchanges are on to see what fork you are on here: https://www.cryptopia.co.nz/CoinInfo/?coin=ZOI

I believe this is normally what checkpoints are for dealing with, but as it seems unlikely anyone will release an updated, checkpointed wallet, I think the best we can hope for is some degree of collective effort to get ourselves all on the same fork.