Amusingly there's a pun here on "Zero-sum Era". This because "rei" is a common way to read the numeral zero, and "zero-wa" (using the same "wa" from the new era name) is the Japanese term for "zero-sum".
No, because nobody cares about the sound. The kanji matters. Soundwise there are tons of kanji with the exact same pronounciation so there is no pun to be found.
Japan has a proud tradition of phonetic based puns, called dajare. Wikipedia has a surprisingly long list, which includes explanations: