How can I share a form created in one account with another account so they can edit it?

Yes it is possible to achieve your requirement by taking advantage of our "Sub User"  account feature. You can share your forms with another user to view / edit forms or submissions. 

You may like to take a look at the following guide which should help you:   https://www.jotform.com/help/232-How-to-Share-Forms-with-a-Sub-Account-User

Hope this helps.

Do get back to us if you have any questions.