Since you have this labeled as tournament quality I felt I should let you know that all artifact lands are banned from modern style tournaments.
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Black sun zenith doesn't help you with Geralfs Messenger. What you end up with is a 3/3 with both a +1/+1 counter and a -1/-1 counter so since it still has the +1/+1 it would still die. The only way (In Standard) to remove a +1/+1 counter is with Hex Parasite.