to the starter solenoid connector near the starter passenger side. This puts 12v directly at the starter and eliminates all the electric circuits including the relay from ignition key to starter. I had a no start problem with my Z and also checked the starter and the relay and they checked good. Problem is with a simple check of the relay with 12v to hear the click might prove OK but under starter amp load the relay can't pass the amps thru the contacts and the starter fails to operate. I'll bet you have a relay issue.
If this direct getto test fails then the starter is at fault when under load of the engine.