│ Error: error listing Zone: HTTP status 400: Invalid request headers (6003)
│
│ with data.cloudflare_zones.domain,
│ on main.tf line 67, in data "cloudflare_zones" "domain":
│ 67: data "cloudflare_zones" "domain" {
│
I came across this as well, and this was returned from a web search. In my case it was incorrectly assigning the old api_key to the api_token. Double check you have this set correctly.
│ Error: error listing Zone: HTTP status 400: Invalid request headers (6003) │ │ with data.cloudflare_zones.domain, │ on main.tf line 67, in data "cloudflare_zones" "domain": │ 67: data "cloudflare_zones" "domain" { │