Nothing can stop them from doing it, other than it being a very serious financial crime.
Banks have to report their accounts to central banks, so a wild 0 appearing out of thin air would get caught in no time. Numbers have to match exactly, so even a 1 cent drift will cause some red light to light up somewhere.
Printing money causes inflation and third world countries tend to already have rampant inflation as it is so governments will not shrug it off either.
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