This is more of an review/comment than a request for any help.
The MKR2UNO adapter board purpose is to allow the use of Arduino full size shields with the smaller form MKR boards.
While attempting to use the MKR2UNO adapter with the MKRZero and an YUN Shield it became apparent that it was not going to be a "straightforward" fit.
The MKRZero when inserted into the MKR2UNO adapter sits higher than the headers of the MKR2UNO adapter. The bottom of the MKRZero is level with the top of the MKR2UNO adapter board headers. When inserting a full size Arduino Shield into the MKR2UNO adapter the shield to prevented from obtaining a good connection because it is hitting the MKRZero Board. This may be solved by using long pin Female headers inserted into the MKR2UNO adapter board and inserting the shield into these extension headers.
This leaves the ICSP header to be adjusted. I am still working on a good solution to that.
The MKR2UNO adapter board is a good idea and useful. It just needs some refinement.
Side Note: Cutting the header pins on the MKRZero is in my opinion not an option. Removing the MKRZero headers and just inserting pins is also in my opinion not an option.
Modifying a MKRZero to "make it work" is just wrong.
Both would allow the Arduino Full Size Shield to be inserted with any issue. Cutting the MKRZero Female Header Pins, removing about 4mm from the pins may not allow the MKRZero to be used in some breadboard. The Modified MKRZero may not make a good connection with the breadboard.
Removing the MKRZero Female headers, would not allow for the use of MKR Size Shields or Proto Boards.