I apparently entered a ZERO on the guide on Form C. in the line for 27B. How do I delete & clear these errors?

If you're using TurboTax Desktop, go to FORMS and Open Form Schedule C.  You can delete the 0 on Line 27b or enter a different amount.

If you're using TurboTax Online, you can delete Schedule C and step through the interview again to let it repopulate, or delete Form 7205 for Energy Efficient Commercial Buildings from your return.  Here's  How to Delete Forms in TurboTax Online. 

@BootsB