If it didn't sell then either;
it was priced too high
ad was crap
pics were crap
Almost every single time I've sold a car the buyer has pretty much just phoned up, asked to see it and bought it. The main reason I feel is that my ads answer every single question the buyer could possibly ask including pictures from every angle including interior, under the bonnet and boot. I'll detail the full service history including when the last one was and what was done and also when the next one is due and which one it is. Cover all consumables to include their current status and when they were last changed such as clutch, tyres and brake discs and pads.
I'll also detail things such a tyre tread depth, known faults with the car and whether my car has had them sorted, tax and mot cost and length left. Include where you bought it and when and also why your selling it and what your moving on to.
Pictures are key. Don't use crappy locations, I'm easily put off by shitty pictures.
If I was buying a zed I would want to know;
Do the axles click?
Does the Bose jump?
Are the RAYS corroded?
When was the clutch changed?
Have the services been carried out correctly?
Are the interior plastics scratched to death?
Does the boot shut itself on your head when you open it?
Is the front end pebble dashed?
So put it all in your ad
And use proper grammer and language. Txt spk is gonna send me running!