Can I perform Dwitiya Shradh for both paternal and maternal ancestors on this day?

Yes, though the primary focus of Dwitiya Shradh is the paternal and collateral male lineage. You may include maternal ancestors who passed on Dwitiya Tithi in the rite, but their specific honour day is Pratipada. If performing for both lineages, the pandit will conduct separate Tarpan sequences — right-hand for paternal, left-hand for maternal.