I am NOT a tax advisor. Do not construe this as anything other than what I might do in a situation that might appear similar. I would do as belgarion advises and lump them into a set time period. Whatever time period I chose, I would be consistent. The key is paying taxes and keeping records to justify why that is the taxes owed. The only way I see that the IRS would know any different is through an audit. If I am paying taxes, I just need to justify why the amounts are correct and in alignment with the rules set forth by the IRS.
This reminds me, I have to talk to my CPA about how mining creates taxable events. Is the creation of the zcash through mining a taxable event? Or would we pay taxes when we sell eventually in the form of capital gains based on a $0 cost basis? I was looking to aim for a $0 cost basis approach.
Remember, if you are selling Zcash to have the USD, then you just need to show the total USD received minus any depreciation of computers and cost of doing business. You just have to show how you arrived at your profits. If you are keeping the Zcash (or selling to buy another digital currency), then the number you give the IRS and pay taxes on initially (if that is a taxable event) will just be the cost basis when you eventually sell. If you are smart and paying taxes, they get their pound of flesh no matter what.