Piccys

I think its about the same in yours but either way an investigation and a change of oil cant go wrong
DO NOT REMOVE THE STANCHIONS[coated slidey tubes]
Not for an oil change anyway,you might damage them trying to refit them[unlikely but why risk it]and a seal change i wouldnt wish on anyone
Least not yourself
Probably 7.5 wt ,same as the Z2's but check the manual first
PIC 1.
Take off the top caps[probably able to undo them by hand, 26mm spanner otherwise
Turn them upside down and pour out the grey coloured slick ,its messy and gets everywhere as you can seen but try to get most of it into a container
Put all the parts on something absorbent
Pic shows it laid out in order
PIC 2.
Clamp or hold the lower upside down and use a 15mm socket[again check your manual to see if thats the same as im quoting Z2 instructions]
You might find the pumping element spinning round,if so use a pencil to jamb it on the inside while you undo the foot nut
PIC3.
Foot nut ,rebound spring and pumping element laid out in order after removal