If you wanted to take a zero transaction cost in the cryptocurrency blockchain, it is impossible I think, but, its nearly impossible somehow. Transaction fees are controlled by the people who always in rush on getting their transaction to be confirmed so that the transaction can be sent successfully in no time. If you would ever use 0 satoshis or 0 gas fee, expect you will wait for 5 years or even more until the blockchain won't be used to send transactions by anyone else.