Believe they are chrome plated 5mm countersunk oval pan-head screws.
Kawasaki.com shows part no. 23019-022 as 5x14 pan-head screw.
Z1Enterprises lists 23019-012 for Z1 (but not KZ1000 ??). Would confirm fitment application before ordering.
Z1E
These are easy to cross-thread and strip.
Good Luck!