In true elo rating systems, 100 is the mathematical lowest rating one can get, a loss when at 100 doesn't drop the rating further; so zero elo rating for all (or any) of these categories would be impossible. However, some algorithms allow rating to drop to zero (chess.com uses glicko rating I believe, but it is very similar to elo with only subtle changes).
Rating floors aside, what would happen if a rating reaches zero? I guess the same as it reaching any other rating ... nothing really; they are just values. Losing would do nothing to a rating already zero, but other than that - I don't think there would be anything "special" about a rating of zero.
p.s. Although the expression, "we can only go up" being intrinsically true with a zero rating sounds like a "special" assessment of the situation. xD
Today i got a crazy thought -
What is just imagine, if and of your game blitz,daily,bullet four player etc.
Reached ZERO rating then what will happen?
IF ANYONE KNOWS THE ANSWER PLEASE TELL IN COMMENTS