Alec,
Check the sway bar bearings - if the Zantia is similar to earlier models there will be two spherical greased plastic/alloy bearings that are SPRING TENSIONED to keep the correct preload and positioning of the sway bar.

If the tension has been reduced they will rattle - and all that is needed for a check or quick fix is to retension the springs to cure the problem.

To do the job properly, tho, it would be advisable to strip, clean, replace any parts that may be damaged, lubricate and set up as per the manual.

If the Zantia is different to earlier models forget all the above.

Best of luck,

Fento