My initial comment is, that no where did the OP mention what we are talking about. e.g. Mains stepped up/down and being recitified and filtered by capacitors. In fact, AC wasn't mentioned at all, just DC. A better description of the problem is in order.
In any event, way back when thermal dime delay relays based on vacuum tube technology were used long ago. Varistors have been used. Resistors in the AC line with time delay short has also worked.
ZCT is bnot recommened to transformers and I don't quite know the reason why. Part of the problem with an inductive load is that voltage and current can be out of phase. A "dimmer" design for an incadescent lamp is much different than "a motor speed control".
For a lamp, you can basically turn it on at whatever place in the line you want and it will turn off at zero to maintain a particular duty cycle.
For a motor, you have to find the voltage turn on point and continue turning the unit on until the next voltage turn-off point because it will turn off at zero current and that could occur just after you turned it on.
Operating into a highly inductive load generally requires some sort of current limiting. Been there, done that.
I have designed an unconventional turn on system for an audio amp. It effectively had 40,000 uf of capacitance, 50 V rail and a 12 A winding (simplified). The design was not quite what I wanted and I really didn't have the space for another relay, but it works. The only problem is if a fuse blows in any of the rail supplies, I have to replace a resistor. The design worked flawlessley when i accedently reversed the position of the output devices. No damage, except the resistor and up to 5 fuses (4 DC supplies and a line fuse).