Count Not Zero is not among the options for ABAP CDS View exception aggregation, but if you really want it you can walk around this limitation.
Lets take, for example, C_StockQuantityCurrentValue (Current Stock Quantity and Value) CDS view. It shows all materials even the one without stock quantity and value.
What if you want to get a count of materials that have stock. Yes, it is possible combining formula and SUM exception aggregation together. For comparison reasons, I added another measure using COUNT exception aggregation.