Let's suppose we created two contracts: Contract A and Contract B.
Contract A is inherit by Zeppelin's standard token ERC20 where as Contract B is inherit by contract A.
Will contract B be considered as another ERC20 token?
No, it will not be a new ERC20 token. When inheriting contracts as you described, only one token will be created no matter how many times you inherit the contracts, as there is only one instance of Zeppelin's StandardToken ERC20.