Actually, City's top 4 league scorer got close to the 65 in 2019/20 - Sterling (20 goals), Aguero (16), Jesus (14), De Bruyne (13). That amounts up to 63. The next highest scorer on that list is Mahrez with 11 goals.
Would be great if it happens but I think it is unrealistic to expect those 4 to score at least 65 goals in total this coming season when Werner, Havertz and Ziyech are all new in the Premier League.
Also, is Ziyech really a consistent goalscorer? Nikki sorta compared Ziyech vs Willian earlier; in the last 4 seasons with Ajax, Ziyech scored only more than 10 league goals in a season once and scored 10 goals or more in all competitions twice. On the other hand, in the last 4 seasons, Willian did not score more than 10 league goals in a season once but he did score 10 goals or more in all competitions thrice. Their goalscoring numbers are not that drastically different.