Using Flatten to create multiple routes for multiple route tables

Terraform HCP Terraform
1

I have a scenario, where I would like to create three different route tables and each of these route tables will have their own unique routing rules. I am looking to achieve all of these in a single resource block.

Below is my main.tf file and the resource block:

resource "aws_route_table" "tgw_subnet_rt" {
  count = local.json_data.create_tgw_subnets_rt ? local.json_data.no_of_tgw_subnet_rt : 0 
  vpc_id = module.vpc.vpc_id
  tags = merge(
    local.standard_tags,
    map(
      "Name", "${local.json_data.environment}_${local.json_data.vpc_type}_vpc_${local.json_data.tgw_subnet_type}_subnet_rt_0${count.index + 1}",    
    )
  )
  dynamic "route" {
    for_each = {
       **for route in local.network_routes  :  "${route.route_table_key}.${route.route_key}" => route }**
    content {
      cidr_block                 = lookup(route.value, "cidr_block", null)
      destination_prefix_list_id = lookup(route.value, "destination_prefix_list_id", null)
      ipv6_cidr_block            = lookup(route.value, "ipv6_cidr_block", null)
      carrier_gateway_id         = lookup(route.value, "carrier_gateway_id", null)
      egress_only_gateway_id     = lookup(route.value, "egress_only_gateway_id", null)
      gateway_id                 = lookup(route.value, "gateway_id", null)
      instance_id                = lookup(route.value, "instance_id", null)
      nat_gateway_id             = lookup(route.value, "nat_gateway_id", null)
      local_gateway_id           = lookup(route.value, "local_gateway_id", null)
      network_interface_id       = lookup(route.value, "network_interface_id", null)
      transit_gateway_id         = lookup(route.value, "transit_gateway_id", null)
      vpc_endpoint_id            = lookup(route.value, "vpc_endpoint_id", null)
      vpc_peering_connection_id  = lookup(route.value, "vpc_peering_connection_id", null)
    }
  }
}

locals {
  network_routes = flatten([
      for route_table_key, route_table in local.json_data.test_routes  : [
      for route_key, route in route_table.routes :{
        route_table_key = route_table_key
        route_key = route_key
        cidr_block = route.cidr_block
        gateway_id = route.gateway_id  
      }
    ]
  ])
}

and there is my .JSON file
“test_routes”: { “route-table1”:
{
“routes”:
[{
“cidr_block” : “X.X.X.X/X”,
“destination_prefix_list_id” : “”,
“ipv6_cidr_block”:"",
“carrier_gateway_id”: “”,
“egress_only_gateway_id”: “”,
“gateway_id”:"",
“instance_id”:"",
“nat_gateway_id”:"",
“local_gateway_id”:"",
“network_interface_id”:"",
“transit_gateway_id”: “XXXX”,
“vpc_endpoint_id”:"",
“vpc_peering_connection_id” : “”
},
{
“cidr_block” : “XXX”,
“destination_prefix_list_id” : “”,
“ipv6_cidr_block”:"",
“carrier_gateway_id”: “”,
“egress_only_gateway_id”: “”,
“gateway_id”:"",
“instance_id”:"",
“nat_gateway_id”:"",
“local_gateway_id”:"",
“network_interface_id”:"",
“transit_gateway_id”: “XXX”,
“vpc_endpoint_id”:"",
“vpc_peering_connection_id” : “”
}]
},
“route-table2”:
{
“routes”:
[{
“cidr_block” : “XXXX”,
“destination_prefix_list_id” : “”,
“ipv6_cidr_block”:"",
“carrier_gateway_id”: “”,
“egress_only_gateway_id”: “”,
“gateway_id”:"",
“instance_id”:"",
“nat_gateway_id”:"",
“local_gateway_id”:"",
“network_interface_id”:"",
“transit_gateway_id”: “XXXX”,
“vpc_endpoint_id”:"",
“vpc_peering_connection_id” : “”
},
{
“cidr_block” : “XXXX”,
“destination_prefix_list_id” : “”,
“ipv6_cidr_block”:"",
“carrier_gateway_id”: “”,
“egress_only_gateway_id”: “”,
“gateway_id”:"",
“instance_id”:"",
“nat_gateway_id”:"",
“local_gateway_id”:"",
“network_interface_id”:"",
“transit_gateway_id”: “XXXX”,
“vpc_endpoint_id”:"",
“vpc_peering_connection_id” : “”
}]
}
},

When I try and execute this code, the rules are adding to only Route Table, however, I would like to achieve the following:

Route Table -1 : Routing Table-1 Rule 1, Routing Table-1 Rule 2
Route Table -2 : Routing Table-2 Rule A, Routing Table-1 Rule B

So basically each route table will have their own unique routing rules. Can somone please help me, I am struck here and I am not sure how to proceed.