As regards withdrawals made between Zaif Exchange and external wallets,

there is a time lag between creating the transaction (the actual withdrawal process from Zaif) and its approval in the bitcoin network (the successful mining by miners).
It might show up in the next block (on average, every 10 minutes), but it might also take several hours, days, or even weeks.。

You might want to set the miner’s fee as higher than the initial rate if you are in a hurry as this might make the approval process relatively quick.