firmware topic

so i finally decide today to try and update firmware so I can run kk,so this is what i am doing.using adb I type fastboot oem reboot RUU which says it was ok then htc screen pops up.then I dl the newest firmware and with out unzipping I drop into my adb file then I type fastboot flash zip firmware.zip{i did rename file when i put into adb] then adb says it couldnt load file.Ive tried unzipping it and still coming up with eras.So im not sure what i am doing wrong