I use the fowlers preserving unit with the jars, lids and clips. 

Pickling liquid as a rough guide is 3 parts vinegar: 2 parts water: 1 part sugar plus salt and spices. The liquid can be boiled on the stove until the sugar dissolves or all just poured on top of the zucchini and hope it dissolves in the preserving unit when it comes to the boil. Jars with well-fitting lids could also work if the zucchini is cooked in the liquid first- but I have not tried this. 

Zucchini

Brown onion
Vinegar
Salt
White sugar

Spices like, chilli, turmeric, mustard seed, coriander seed, fennel, peppercorns, star anise or whatever combination you like, fennel and peppercorns

Slice zucchini into a 5 ml slice. Peel and slice brown onion into a 5 ml slice. Use about 2 tablespoons of salt per kilo of veg and salt the veg leave to stand in a strainer over a container or sink for at least 2 hours (to remove some moisture). 

Pack veg’s into preserving jars with spices and pour over pickling liquid. Put lids on. And bring to boil in preserving unit (or a pot on stove) boil for 5 minutes and leave to cool in the water.