Currently, Zephyr for JIRA does not let you customize the columns seen on the Test Cycle Summary screen. However, you can add and remove columns from the ZQL Test Execution Search reachable by clicking on the Test Cycle name in the Test Cycle Summary Screen.
1) First Select the Test Cycle Name from the Test Summary screen
2) You will now be in the Search Test Execution screen with a pre-populated search filled with the executions of the selected cycle. You will be able to add or remove from a fixed selection of columns, ie: priority, version, cycle name, project name, and creation date, etc.
Adding and removing columns:
Note: Changes to the columns of a filter will not propagate the change to other filters. New searches or filters will also start with the default column layout.