With a triac, YOU need to identify the turn on point, and pulse the gate momentarily - then the triac will drop out by itself at the next zero crossing. This is why triacs are good for trailing edge control.
With an SSR, don’t use one with built-inzero crossing detection...
Again, YOU need to detect the zero crossing points, and turn on/off whenever you need to.
In both cases, keep in mind the electrical noise generated by switching on the waveform.