Hello,
If you plan to use a commercial fertilizer product, for zucchini a balanced granular or water soluble formulation, 20-20-20 or other preparation where the ratio of NPK are the same. Cucumbers need less nitrogen so a product where the first number -N or nitrogen is lower than the P(phosphorus) and K- (potassium).
An organic granular slow release product could be used or a generous side dressing with good compost if an organic approach is wanted should supply the needed nutrients to either zucchini or cucumbers.
Hope they do well for you and you are overrun with zucchini
Karen O