Hello and welcome
Sorry to hear of your problems but it's somthing most diesel 75/ZT owners have to do at some stage.
With that milage it may be a good idea to change everything in the clutch system at the same time..Master cylinder slave cylinder and clutch.
Take advice from the guys on here on the best parts to get fitted.
I see you are in Belgium some of us are visiting the Best of British show at Boxtel NL in a couple of weeks why not come and say hello. Someone may even be able to find some more horses in that engine.
regards Ian