I keep thinking an old iPhone would do a job.
Just what I use! An old iPhone that you wouldn’t use.
Hidden away in the car but connected to an ignition switched supply. It’s left on (in fact the off button doesn’t work on mine - if if some scoat finds it they can’t switch it off). If it goes flat as it’s an iPhone it starts when re-powered.
Set up another iTunes account.
Turn off all apps, notifications except for FindFriends and share that with your account. Put the phone on silent.
Put in a cheap sim with a minimum amount of data. I use a £3pm contract sim from Vodafone. Make sure it gets a phone signal and gps and test.
There you have a cheap tracker device.
I use this in my Discovery. Am sure you could find a location somewhere that you could hide it in a Zed - maybe under a seat.
Find your device and set it to notify you if it leaves that location. Not just a tracker but an alarm.