In a colander, place the onion, garlic and chilli along with a tablespoon of salt. Scrunch with your hands, then allow to sit for 1 hour.
In another colander, place the zucchini and cucumber with the rest of the salt. Toss it, then leave it to drain for 1 hour.
In a large saucepan add the vinegar, sugar and spices. Bring to the simmer over a medium heat then add the softened onion mix. Bring to the simmer for 30 seconds then add the zucchini and cucumber mix. Return to the simmer then take off the heat.
Spoon into sterilised jars while hot, seal and chill.