Can a shredded body like Zyzz had be attained without the use of steroids? Actually can you get shredded at all without steroids?
If by shredded you mean:
Yes, you can do it naturally, but it's rare. It also depends on whether you expand your definition to "illegal substances" like off-label ephedra use or clenbuterol. Most folks (natural or otherwise) who want to look shredded do so for competition times and go through cycles of "bulking" and "cutting".
The lower your body fat gets the more insulin sensitive you become, and the quicker your body is to absorb fat. Maintaining an extremely low body fat (<5%) along with highly developed muscles, year round, is borderline impossible without illegal substances.
~10% body fat and a rather "jacked" figure? Totally do-able naturally with a lot of work and maintenance.
To address some of the comments regarding insulin and body fat, I'll extend this answer out a little further. First, with peer reviewed research of a large study group:
Conclusion: Lower-body fat mass is positively associated with an estimate of insulin sensitivity independently of trunkal fat mass in both lean and obese middle-aged men and this effect could partly be statistically explained by variations in serum adiponectin levels.
One of insulin's largest jobs is signaling to fat (adipose) tissue to open the doors and allow fat storage to occur. On the surface it seems like being less resistant to insulin (not storing fat) would be a good thing, but indeed this is far from the case. That free floating fat that is not being absorbed properly is now being stored around organs. It is also clinging to the blood pathways, forcing smooth muscles to contract more which increases blood pressure, loading a heart that is by now wrapped in fat.
The field of endocrinology is vastly complicated. For anyone interested in further reading I'd recommend Sapolsky's book Why Zebras Don't Get Ulcers.
I partially agree with Eric. Zyzz wasn't at a level of <5% bf, he was around a 8%. You can achieve that level of definition without taking steroids. As Eric says, being in a 8-10% bf is totally possible with hard work.
But first you have to consider two different things. One is your bf level and the other your muscle development.
As said, you can achieve a 8%-10% bf level without steroids, but if you want to be under a 6% probably you would have to take something.
The same with muscle development. This depends more on your genetics and the ability of your body to gain muscle, but you would probably reach a limit where if you want more muscle you would have to take something too.
Zyzz's body wasn't a highly muscle developed body, his strength was his genetics, which provided him a really good looking body with a very nice shape. But Zyzz was an ectomorph and had it very difficult to gain muscle. Someone with better disposal to gain muscle as a mesomorph and with also good genetics could achieve that body without taking steroids.
So, asking to your question now. If you refer with "shredded" to the low bf level, yes, it's possible. But if you refer to the entire body looking, you have to consider what I've said about muscle development.
To give some examples of body building bodies without steroids I would recommend the field of natural body building. You can't always prove, that none of these uses steroids (see nearly any other pro sport), but it's a start.
Here is the Homepage of the swiss Federation: http://www.snbf.ch/
Or here an english page: http://www.naturalbodybuilding.com/
In contrast to the picture of Zyzz, most of the pictures are from competitions and therefore the athletes are "painted". Also, as far as I can see, these are season pictures, while off season they do not have their bodies likewise defined.