* Direct Comparison: A bull is a male cow, and an elephant is a large mammal. A zebra is also a large mammal, but the connection isn't as direct.
* Possible Analogies:
* Stripes: You could say "Bull is to elephant as zebra is to horse". Both zebras and horses are in the same family, and zebras are known for their stripes.
* Savanna: "Bull is to elephant as zebra is to lion". This connects them all to the African savanna ecosystem.
* Size: "Bull is to elephant as zebra is to donkey". This relates them by size comparison (bulls are smaller than elephants, zebras are smaller than donkeys).
It really depends on the specific aspect of the relationship you want to emphasize!