I AM right, because I've done it myself.
His exact same situation, except I took my Corrado over to Germany. Soldiers take their cars into and out of Germany every day. I helped people with their inspections all the time. I helped my soldiers export their vehicles as part of outprocessing all the time. It's 100% military, including bringing a euro spec vehicle back to the states with you, providing it's 25 years old or older. I brought back a German Rabbit Convertible with my Corrado's engine in it.
So I have personally:
-Taken a us spec vehicle into Germany.
-Swapped that engine into a euro - spec car, got it to pass military inspection, AND had it TÃœV'd.
-Brought that modified euro - spec car back to the states and got it titled with NCDMV.
OP, take the Z, you'll be fine, even with mods. You can bring it back with you no problem, but you may sell it when you find out how much money you could potentially sell it for - pm me of you want to know how the Zollamt works. Buy a $500-1000 daily beater when you get there for a dd. You'll be glad you did.