Hi,
please look at this example Example MPC5775K PinToggleStationery S32DS
I tested it and it works correct. I call function boot_cores to run both z7 cores instead of hw_init function. But do not forget look to the startup.s file. In default project, hw_init function is called before you jump to the main function.
This is the screen of z4 core. You can see that both z7 cores started to run

When you click on the marked line, you can watch z7a source code

and also z7b source code

PS: S32DS has a problem with "one line" while loop. If you have for example this code:
while(1)
{counter++;}
and you click on step over or step into, debugger stop working and it may seen the core is not running correct.
I hope this issue will be fixed in the next release.
Regards,
Martin