AVERAGE - Multiple VLOOKUPs whilst ignoring zeros or blanks

See attached Excel doc for example.

I do some reporting for a contact centre and a report I'm trying to build looks at agents wrap targets. This report uses averages and prints a percentage for us to look at and whether they've met the weekly % target. However I'm struggling to make the overall % (under 'Summary') truly accurate as it takes into account any zeros.

For individual agents I need a similar formula to what I already use, but ignores zeros or blanks.

Any help would be appreciated.