Things have changed recently on this front. Since the last week, 100% of your sale proceeds from stocks sold (from holdings) will be available on the same day, This is because Zerodha does early pay in of stocks.
Check this announcement - 100% sale proceeds from selling holdings will be available for trading from October 7, 2024
Note - Early pay-in is when you fulfill your settlement obligation (funds or securities) to the Exchange earlier than the designated due date for the particular settlement.
However, settlement of profits from option trading and intraday trading are settled the next day of the trade.