http://www.zazzle.com/gifts?ch=rangersjunkyard this is the actual offender to be going after, the one who claims to have designed the shirt.

http://www.zazzle.com/mk/policy/designer_license_agreement here is zazzle's agreement with "designers", aka people who create stores and upload their designs to. Rather plain and simple, about halfway down the page it lists the items that are prohibited, and among them is:

You may not use copyrighted material.

and

If you do not follow the rules set forth above, Zazzle may:
Delete the Product(s)
Suspend your Designer account with Zazzle ("Account").
Terminate your Account.
Withhold any Earnings for Products that contain inappropriate or inaccurate descriptive information.
How does Zazzle enforce these rules?
Zazzle may take the following actions to enforce the terms of this Agreement:

Send a notification informing you of the offending action, behavior, tag, spam or description and request that you take corrective action immediately.
Make your Product(s) unavailable.
Delete your Product(s).
In the case of certain repeat offenders, we will, in our sole discretion, withhold payment of your Royalties.
In the case of certain repeat offenders, we will suspend and/or terminate your Account.

Or, in other words, fairly standard procedures are all that is needed here.