I found errata between Arduino IDE's pin definition and on-board silk indication on ULTRA Zero.

The mis-arrangement are found between D0 to D4 and details is shown in the following image.

This difference can be aligned to "as written on board" if you have a chance to re-write firmware by Arduino.org's Arduino M0 (But it is not convenient since not main-stream so far..) Sorry inconvenient but please refer this image for your programming and prototyping.

Thank you,