Primarily是状语 ,
the banker-customer relationship是主语
is是系动词
that of debtor and creditor是表语 that是指示代词 代替前面的 relationship
后面是 并列的句子 relationship
-- who是主语 is 是系动词 which是表语
depending on whether the customer's account is in credit or is overdrawn.
是现在分词短语 作状语 whether the customer's account is in credit or is overdrawn是宾语从句
作 depending on的宾语 .
句子意思 银行与储户间的关系主要是债务人和债权人的关系
——谁是债务人或债权人 取决于客户的帐户是有结余还是透支.