Hi Batiste,
We do not have a specific DDOS attack, especially as ZAP is not distributed.
However a ZAP active scan can put a significant strain on websites so if your site struggles with just one ZAP instance attacking it then it will _really_ struggle under a DDOS attack.
You could always launch multiple ZAP instances to attack the same site, but you would be constrained by the system they are running on unless you launched them on different systems.
We do not have explicit support for that but ZAP is designed to be easy to automate so there will be lots of 3rd party tools which can do this for you.
Cheers,
Simon