Overview
To track the incomes and expenses, you need to assign a category to your transactions[1].
Important
Reports are valued in USD (and not in ZEC).
Therefore you also need to have the price of 1 ZEC at the time of the transaction.
If you initiated the transaction and entered the price of ZEC in the "Send" form. When you receive ZEC, the transaction has "N/A" price. It should be edited in the transaction details page.
Fetching Tx Prices
For convenience, the market prices can be retrieved from CoinGecko for the current year[2].