Concurrent Zoom meetings - 1 Business Account, 4 Licensed Users

Each user can host meetings independently and simultaneously of one another on an account. User A and User B can both schedule meetings for the same date and time, and should have no issues running them at the same time. 

The support article regarding concurrent meetings says: "Licensed users on Enterprise, Business, and Education accounts can host up to 2 meetings at the same time." This means that each licensed user on those account types can host up to 2 meetings at the same time, independently and simultaneously of one another.