The natural flow is 

• Lead (no value yet), 
• after qualification you may be able assessing a value. 
• Then you want to convert a lead into a Potential (note that you cannot enter a $ value into lead, i.e. if you have a $ value you need to create a potential)
• But of course you don't want an account yet because an account is a customer and your lead isn't yet 

When trying to convert a lead into a potential Zoho automatically creates an Account.

How do I convert a Lead into a Potential without creating an Account?

A Lead has not $ value

A Potential has a value but not all Potentials are Accounts

An Account must have at least one "closed potential" but can have many open potentials.

In other words: to become an Account at least one "financial" transactions must have happened. That may not be the case for every potential.