One thing is that OCaml modules are first class objects, so can be constructed at runtime and passed around as variables. But this Zig example, I think, will cover the most common case of functors for creating generics.
(I'm also not sure if Zig does compile-time check if the type T is compatible with LinkedList. OCaml does this type of check, making sure the signature of T fits the requirement of the functor LinkedList. The module T may have certain functions, for example a compare function associated with T to ensure sorting of the elements in your data structure.)
(Not even close to a zig expert, but I've been playing with it a little bit, find it very interesting, and think what I'm about to say is correct:)
The zig equivalent of a module, a struct, is also a first-class object in zig, so should be the same as OCaml there.
However, Zig does not have anything like a signature -- in that sense, it's "dynamically typed" at compile time (i.e., like type args to C++'s templates, however not nearly as bad because the errors you get are immediate and understandable -- think of it as more like "I fucked up the types and got a python-style error" than I "I fucked up the types and got a C++ templates error").
(I'm also not sure if Zig does compile-time check if the type T is compatible with LinkedList. OCaml does this type of check, making sure the signature of T fits the requirement of the functor LinkedList. The module T may have certain functions, for example a compare function associated with T to ensure sorting of the elements in your data structure.)