Dzeko is certainly not a bad player, but does not come close to the level of Lukaku. I think he's a lot older too. Lukaku is more explosive, faster, more dynamic and also scores a lot more. But it's better than nothing. And maybe he will do well at Inter. Or maybe Lukaku will just come back just like in the past.
They are players from different generations and you can not compare them like this. Dzeko has 85 goals in Serie A. If he can score 15 more goals, he will join the 100+ goals club that is not easy to get a spot in. In 2016–17 season, he scored 29 goals in Serie A and he has two other seasons, 2017 - 2018, 2019 - 2020, with 16 goals.
If I only look at stats of goals, I don't call Dzeko is worse than Lukaku.
https://en.wikipedia.org/wiki/Edin_D%C5%BEekoWhat you say is true, Edin Dzeko is one of the strikers who is quite good especially he has scored almost 119 goals from a total of 260 matches in all competitions while playing for roma, but as we know now Edin Dzeko is 35 years old and of course the performance and his stamina has decreased enough, will he be able to replace Lukaku role as the spearhead of Inter Milan in this season?
Inter Milan get troubles and they can not find better striker with limited time and restricted transfer budget. Top strikers are in big clubs and they won't move to Inter Milan. Dzeko is a replacement for Lukaku in one or two seasons before Inter Milan can find a younger and better striker.