I am wondering whether the self destruct on perimeter trip feature actually permanently bricks the Zymkey or not.
In other words if the tamper detection is tripped do you need to replace the entire module or just reload the cryptographic keys?
I would test this myself but they are not cheap to replace! 
@josephmarsden
Zymkey 4 has two modes of operation for Tamper detect.
1. Production Mode (Tab Cut)
IF (tamper detection is tripped AND self destruct mode is configured AND the lock tab is cut) THEN your Zymkey is a brick. When in production mode the unit is intended to self destruct if breached.
2. Development Mode (Tab not Cut)
IF (tamper detection is tripped AND self destruct mode is configured AND the lock tab is NOT cut) THEN your Zymkey continues to be usable. This is intended for development work, so you can test your physical security, repeatedly. When in development mode you might find the notify configuration more useful.
Okay, makes sense. Thanks.