Being very successful in a saturated market is definitely possible, especially if you have a product that's much superior to your competitors. However, I don't believe that you do, especially as fashion is quite subjective and you'll struggle to have an empirically better product.
The t-shirt space is very crowded - it sometimes feels like everyone in the world now owns a t-shirt company - so there really is a hell of a lot of competition.
I don't see how your company differentiates itself from the others and its branding, something I perceive as quite important in the fashion industry, seems quite weak, despite the quite catchy name, especially when you're competing with bigger long-established names in the area that advertise heavily.
You'll likely be a modest success, but your designs are, in my view, largely quite forgettable. I think the high-quality arty designer t-shirt angle is a better, more profitable, higher-margin long-term direction than the more passé low-end "cartoony" or "humour t-shirt" market that you're focusing on since they both utterly sewn up by big names, overly saturated and a completely cliché. I do quite like the zombie t-shirt though.