It is possible to combine "count" and "for_each" in a terraform resource block

But you have to be "dynamic" about it

Here's an example of what I have in place (and working)

resource "azurerm_network_security_group" "nsg-001" {
count               = var.nsg-deploy.deploy ? 1 : 0

dynamic "security_rule" {
    for_each = local.nsg_001_ruleset_001
    content {}
}

Cheers

-=A=-

.