The Zulu Three HEIR and Zulu Four HEIR are equipped with a front thru axle. Here's a guide to installing your front wheel securely with the thru axle.
Step 1: Insert Wheel into Dropouts
The brake rotor goes on the left side of the bike (if your bike is new, there may be a plastic protector between the brake pads - remove that protector before installing the wheel)
Make sure that the brake rotor slides between the brake pads.
Make sure that the hub is fully inserted into the drop outs. You will know it is correct when you can look through the drop and see through the center of the hub.
Step 2: Insert and Tighten Axle
Insert the axle from the left side of the bike.
Attach the thru-axle nut to the right side of the axle and tighten.
Tighten the quick release handle
IMPORTANT: The Quick Release handle must be firmly closed and tight. Adjust the tension by loosening of tightening the nut on the right side of the thru-axle. It should require firm force to close the quick release handle and it must be fully closed. MAKE SURE THAT THE LEVER CANNOT COME IN CONTACT WITH THE BRAKE ROTOR - the best way to insure this is to make sure that the nut is tightened correctly and the lever is pointed backwards so that the brake mount is between the lever and the brake rotor.
IMPORTANT: Regularly check your axle to make sure it remains fully closed and tight.