The main difference is the pickups that come standard with each bass. The Z3 comes with the Super Fatty 2 pickups, which are my favorite pickups I've ever heard on a bass, and the the ABZ comes with the FDV pickups. The FDV pickups are made from AlNiCo and sounds like a J pickup on steroids. The Super Fatty has neodymium magnets and I can't word it better than their website does so here's a quote:
"They feature an end to end humcancelling coil array with neodymium magnets and hardened steel poles. The coils are noise-symetric/tone-asymetric, which means they maintain near-perfect noise rejection with increased low-end clarity. They have been designed to combine Super clarity on the B and E strings with increased warmth and Fatness on the D and G-strings. Their tone has been described as very clear and transparent on the bottom and very smooth and punchy on the top. They they have a natural overdriven quality when pushed hard that is similar to a vintage tube amp."
However, you can change up the pups on either bass depending on your taste. Just depends if you have the money. The Z3 usually costs more. The ABZ is a passive bass, while the Z3 is has an active/passive toggle. ABZ uses swamp ash while the Z3 uses a special technique of dual density swamp ash.
TL;DR and biggest tip: Email them/contact them through the website. They're a huge help and respond quickly.
