Referring to your previous thread (because you've hidden or omitted component values, erasing information in this new version of schematic), the R and C values are such that the middle-side gate node follows the bottom side switch reasonably quickly.
In the instant of turn-on, if nothing else the zener shunts the capacitor charge through the switch, and drain voltage follows source voltage (because Vgs is high, saturating the middle-side transistor). It is probably intentional that the low-side switch absorbs somewhat more turn-on energy than usual, due to this; it should be heatsinked accordingly.
In the instant of turn-off, the middle-side transistor turns off gradually. Whereas in a regular common-source gate drive situation, the gate can be driven quite hard; in this case the middle-side transistor is driven off by drain current, so, probably not very fast/hard (depends on turn-off current; 100s mA minimum?). Its gate voltage also rises gradually over time, due to the RC circuit connected.
Preferably, the RC circuit matches the time constant of the drain voltage rise, and low-side turn-off, so that Vds's are reasonably closely tracked; there is some room for adjustment here, and again, rate will depend on Id(pk).
Worst case, the rates don't track, and one or the other ends up avalanching briefly; this isn't really a killer, it just increases switching losses a bit. Enough that you need to design for it. A worst case design with generous heatsinking isn't a bad idea, but it can be improved through these adjustments, and range testing.
Tim