The short answer is no:
The temperatures that the cold water is preheated to are below the Legionella growth range.
There is no hold up of any water in troughs or tanks - it is constantly exchanging heat then going to drain.
There is no residual hold up of waste water in the Zypho unit as it has a built in angle to drain out. Provided it has been installed with a spirit level as per instructions, no stagnant water can ever build up.