Possible duplicated costs: Expenses VS COGS

We are a manufacturing company. When we created our items in Zoho Books, to use the inventory function, we assigned to each item a COGS value. We also register in Zoho Books tour purchase of raw materials as Expenses. We have now detected that our total monthly expenses seem to be duplicated (COGS + Expenses) Therefore, since we manufacture ourselves and we don´t purchase finished goods, we have decided not using the COGS values anymore and work only with expenses. Is there any way to delete all the COGS values from all the previous transactions?

Thanks in advance for your help,

Regards