In D&D 5e it appears that willing creature is defined by "consent". Zombies essentially have no will unless under control, but while they are under the control of a necromancer, can they be willing creatures for the purposes of spells?

This would perhaps be better as an addendum to Can you make an unwilling creature willing? In other words, what defines “willing”?, but that question does not discuss the undead, and neither do any answers to it.

_{note: For dominated creatures that could otherwise consent, this is complicated, and this question does not address that.}