How is the "0" that the Vlookup returns defined

There are instructions at the top of the page explaining how to attach your sample workbook (yellow banner: HOW TO ATTACH YOUR SAMPLE WORKBOOK). Screenshots are of little practical use as we cannot manipulate them.

A good sample workbook has just 10-20 rows of representative data that has been desensitised. It also has expected results mocked up, worked examples where required, relevant cells highlighted and a few explanatory notes.

Administrative Note:

Although we value your privacy as much you do, it could be important that members have a rough idea of your location as the solutions they offer may be affected by your locale. For instance, you might in the future post questions which are related to your regional settings.

With this in mind, please update your profile to something more precise (something such as UK, Europe, USA, UAE, etc. will suffice).

Thank you for helping us to help you.

No, it's not clear (to me), but you could try this:

=IF(OR(ISNA(BZ15),BZ15=0), ...

Glad to have helped.

If that takes care of your original question, please choose Thread Tools from the menu link above and mark this thread as SOLVED.

Also, if you have not already done so, you may not be aware that you can thank anyone who offered you help towards a solution for your issue by clicking the small star icon (* Add Reputation) located in the lower left corner of the post in which the help was given. By doing so you can add to the reputation(s) of each of those who offered help.