Shift-register circuit chronogram
It's hard to tell, but it looks like your ini pulse comes just after the clock's falling edge. If you make that pulse a little longer or move it to the left just slightly to be active during the clock transition, you'll get the results you expect.

EDIT: I'm sorry, after taking another look at the system, it seem that ini does in fact work as intended. When the ini pulse comes, Z2 does clear (it reads 00h briefly), but on the next active clock edge it receives the value sent in from Z1 (0Ah). I'm not familiar with this type of register, but it seems like it's working.