His goal scoring rate in the PL was 0.62 gpg. Harry Kane's was 1 gpg. He was a long way off elite in the PL.
Zlatan during December last season was actually very near to the top scorer of the league, may be one or 2 goals less, than Lukaku is now to be fair and honest, even though he missed many chances at this time as well.
His performance started to drop heavily after the ban he got against Bournemouth, but before it he was nothing short of brilliance to us. He peaked in EFL cup final but that match seems to have left him with no more fitness for the rest of the season.