This time I edited your question for you. Next time, please use the tools explained on this page to make your question more readable.
You might consider using max three times, instead of sorting (although that might not make much difference, it will depend on your data characteristics).
Another small tweak: you don't need find, since you can use ~any(z) and use z directly to index the result.
A final remark: you code looks like a change in algorithm would probably result in a much more substantial speed increase. I'm not entirely sure yet how, but I suspect there is a possibility for a different setup.
It would help if you either attach your data in a mat file, or write code that will generate plausible data.
