Mixing AVERAGEIF() with OR() & AND()

I'm having the issue where I need to mix an averageif, with multiple conditions, some OR and some AND.

I've started with:

=average(AVERAGEIFS(AI:AI,U:U,"Photo",D:D,"July 2013"),averageifs(AI:AI,U:U,"Photo",D:D,"Aug 2013")), but this doesn't average the full set together.

The logic I need to accomplish is, average range AI:AI IF U:U=Photo AND D:D="Aug 2013" OR D:D="Jul 2013"

Any ideas?

Thanks in advanced!
-G