Investment in general does not have zero risk. Investment in crypto definitely does not have zero risk, even Bitcoin does not have zero risk. There are risks involved with holding bitcoin for a long time. There is the risk of theft (this could include cyber attacks), there is the risk of a misplaced seed phrase, and there is also the risk of a bitcoin crash, however small the chance might be. As long as there is a possibility of loss, then there is risk. It doesn't matter if it's a 0.5% possibility or a 70% possibility, as long as there is a chance, it can not be "zero risk".
You can say bitcoin has "low risk", and you can even say in relative to other investments, it has less risk, but it does not have zero risk.