Guess the designer wanted to come up with something similar to the style of the U's and S's. Nah, that is fine with me; I would not have used the lowercase F for francs though.
Here is another odd zero, from a presumable design for an Andorran €2 commem* to be issued this year. Yes, that piece commemorates a 600th anniversary.

(* As we all know, there is no way to throw a country out of the EU. But Andorra is not even a member state, hehe.)
Christian