Heat 5 tbsps oil over a gentle heat in a large heavy pan and sweat the onions until they start to soften. Add the ground spices and cook gently for a couple of minutes.
Add the garlic and squash to the pan, stir together and cook for a few more minutes before adding the stock, chickpeas and orange zest. Partially cover and simmer for about 15 minutes until the squash is tender.
At this point check the consistency. If the tagine is very soupy pour off some of the liquid into another saucepan. Boil until reduced then return to the pan.
Add the orange and lemon juice and stir. Just before serving stir in most of the corander and pour into a serving dish. Scatter over remaining herbs and serve.