The Grammatical Subject of Philippians 1:21

Ἐμοὶ γὰρ τὸ ζῆν Χριστὸς καὶ τὸ ἀποθανεῖν κέρδος. (Philippians 1:21)

A question that arises from reading this scripture: is the grammatical subject τὸ ζῆν or Χριστὸς? Max Zerwick (Biblical Greek Illustrated by Examples) explains that either term could be the subject, but he favors τὸ ζῆν in this context, and I agree. But others say that Χριστὸς is the subject, even though it lacks the article. While I think the reasoning is wrong--Χριστὸς is not the subject, but rather, it is the predicate--I emphasize that Χριστὸς could be the subject as Zerwick states and it does not have an article.