I’m looking for a way to update The Card Holder Name, Card Expiration and Billing Zip for cards on file (using the Card ID as the identifier similar to disabling a card).
I have been able to create customers, create a card for a customer, and disable the card. I have not yet found a way to update these via any REST endpoints mentioned.
The closest I have found is that it is possible (or at least used to be) when looking at this webhook detail:
https://developer.squareup.com/reference/square/cards-api/webhooks/card.updated
which mentions “Published when a Card is updated by the developer using the UpdateCard endpoint.”
Any help would be appreciated thank you!
There isn’t an UpdateCard endpoint cause we generally update the information on our end when we get the information from the card network. 
Thank you for the information Bryan. That is good to know.
I’m working on implementing Square the same way we offer Stripe to our customers who prefer Square. 
Our customers offer services they offer that their end users can then purchase. (Essentially we are their custom shopping cart solution). They authorize us to create payments for them, and we let their end-user supply card information to you directly (thus the API and creating customers for ours).
We offer a UI where their end-users could update card information should they need to update it but just the information in my original question.
But in this case, I will either let them just delete the card that you stored and create a new one instead of being able to modify an existing card, or disallow their customers from being able to save credit cards.
Thank you again.