irule to remove part of uri and combine uri

Try this

when HTTP_REQUEST {
    if {[HTTP::uri] starts_with "/content"} {
        set field2 [getfield [HTTP::uri] / 3]
        set field3 [getfield [HTTP::uri] / 4]
        set mergedFields ${field3}-${field2}
        set removeContent [string map [list "/content" ""][HTTP::uri]]
        set newUri [string map [list "${field2}/${field3}" $mergedFields][HTTP::uri]]
 
        HTTP::redirect https://[HTTP::host]$newUri
    }
}