I couldn't find a support-thread for the ZipShip shipping-module (other than a couple that have been closed), so here we go ...

I've just submitted v2.0.0 to the plugins for review; it's been tested under Zen Cart 1.5.4 and 1.5.5 but should be OK for earlier versions, too. The following changes were incorporated:
  1. Use PSR indentation
  2. Add "extends base" to class definition
  3. Rename constructor to __construct for PHP 7+ usage
  4. Don't enable the shipping method unless the current ship-to address is configured for the method.
  5. Change usage of the PHP "split" function for PHP 5.3+ usage (it's deprecated).

Note: This version of the ZipShip shipping module is also needed for compatibility with the One-Page Checkout plugin.