I want to start a new block chain and mine the 0th block, but I guess the hardcoded checkpoint in chainparams.cpp won't allow that.

I guess I need to reset the checkpoint hardcoded as follows before starting a new blockchain.

    checkpointData = (CCheckpointData){
        boost::assign::map_list_of
        ( 0, uint256S("000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943")),
        0,
        0,
        0
    };