Average columns across multiple sheets

[Stayfair]

I have 10 sheets in my workbook that represent 10 employees. Column G, rows 5 through 739, represent the amount of time each employee spends doing a certain task for each day of the year. All these cells have zeros in them until a we come to that day and a time is entered for that day. The result in each cell is a certain amount of minutes spent on that task.

I can average each employees time individually on it's own sheet with this formula: {=AVERAGE(IF(G5:G739=0,"",G5:G739))}, but what I'm having a problem doing is averaging all 10 employees together on a separate sheet. I'm trying to figure out company wide how much time is spent on this particular task each day.

My depth of understanding here isn't too great, I'm learning as I go. I think I have to incorporate that formula while also selecting each sheet. I'm starting to get the BSOD in my head with this one.

Hopefully I've given enough info that someone can help me through this. Probably a basic problem for most of you, unfortunately, not for me.

Thanks.