The large things always hide in clear view!
You have two options:
- cook it with a meat or veg filling and freeze it. This can work well as, though frozen, the taste matures, more than balancing the loss of texture following freezing (i.e. it goes a bit squishy)
- leave it in a cool, dark place until you get home and want to cook it. A marrow easily keeps for that time, courgettes may be a bit marginal.
How much spare cooking time do you have before you go away?