Oh I definately agree...please don't have him put down for this!! From the details of the event you described, this was not an all out attack with intentions to disable or kill..more like a warning. I agree that an attack would break the skin and draw blood. Surely this is not something serious enough for Zeus to lose his life for. :(
Also, a side note about Sheba, who is Xena's sister (my baby). She was resting comfortably on the sofa one afternoon right after almost 2hrs of playing with my kids in the yard. My son, who was 9 at the time, flopped down on the sofa next to her and went "arrrgghhh" in her face. She snapped at him, breaking the skin under his chin (tooth mark) and chipping his front tooth. It scared the bejeebers out of my son, BUT, he was knowledgeable enough at the time to tell us it was his fault for "harrassing" her. As upset as my mom was, she was confident that this would be an isolated incident, and thankfully, it was. Sheba is almost 10 and is the gentle queen that her sister Xena is. She LOVES my son and he loves her just as much.

Only you can decide wether this is a good "match" for you and your family. If re-homing him is an option for you (EAO76 has made an offer!!), and that's what you want, then by all means, but I really don't think that Zeus should be euthanized for what appears to be an "accident". Good luck & (((HUGS)))!