Question related to TVS Diode in series
Yes you can put two bi-directional TVS diodes in series.  They also supply parts well over 600V.

Perhaps your uncertainty is due to choosing unidirectional symbols.



I just checked your part number. The TSPMF4L30A shud be TPSMF4L30A which is unidirectional (Zener) and not bi-directional.  

Using them as you have shown is equivalent to using a single 400W unidirectional TVS with 60V  Voltage - Reverse Standoff (Typ)