How to put buy order, stop loss order & target sell order on zerodha trading platform simultaneously?

You will have to use bracket orders: http://zerodha.com/z-connect/tradezerodha/zerodha-trader-software-version/bracket-orders-trailing-stoploss-sl., but this is an intraday product. The other option is to place it individually manually using NRML/MIS, but two issues doing that: 1. Margin is required as if it were 3 orders. 2. If one of them get hit, u will have to continuously monitor. The flip side of brackets is that it is only for intraday.