Question

If zinc is more reactive than copper then why is placed after the copper

Answer 1

Zinc has a greater nuclear charge but the outer shell electrons are in the same shell.

Zinc has last sub orbital as
4s2
which it gives willingly to become electronically stable. Also, zinc's pull on its last electronic shells is much less and is hence more willing to combine.
Copper has a last sub-orbital as
4s1
which decreases its capacity to form bonds like zinc. Ideally, copper should form more bonds but due to lack of electrons in the last shell, it cannot form many bonds.