man that z bugg is a pesky lil sucker isnt it?
i would keep your current z while you work on the other,that way when you start to get tired of working on the new one or even getting impatient and having doubts(which never happens to anyone whos ever had a z project)
you can hop in your RUNNING ,fuel injected,6speed manual,300+ ft lbs of torque shiny, fast zcar and love every minute of it aswell as provide some inspiration for the other(or to help set bigger goals)
good luck trying to sleep now