These are enormous and awesome events, the falling of Shamayim, ץ to צ, and ם to ת. We write צ"ץ as it happens suddenly, and ת"ם, as it is the end of something.
It happens suddenly yet also it takes time, until the original ץ, which is ה years after ת"ם. In short, צ"ץ ותמ"ה.
It is the end of the 288 sparks of Kedusha, four times 72. They are being returned to their source. At the end of צ"ץ ותמ"ה, mankind finds G-d, everlasting.
