Probably been asked before ................
Yep - one of the joys of Zed ownership.
Firstly, you need to establish if it is from door window seal or windscreen top seal.
Start with the basics and check the rubbers to see if there are any cuts or tears. Rubber seals should be treated on a regular basis to keep them in a supple condition and give the best seal. I use Gummi Pflege but Halfords do an equivalent and there are others.
If the leak is from the screen the usual suspects are the A pillar `triangular' plugs which you can see when you open the hood. Give these a squeeze - if they ooze water that's the problem. These plugs can be dried out and re-sealed with silicone rubber, did mine 4 years ago and they have been tight since - job takes about 30mins (they'll probably leak againtomorrow now I've said that!).
If the leak is from the door windows then there are adjuster bolts under the lower door to alter alignment and pressure.