First of all two of five valves (zones) with spontaneous failure sounds odd to me.
You have obviously established that there is water flow to the valves, correct? You had to shut off a hand valve to replace the Rainbird valves? When done, you turned the valve back on? The electrical sounds like it is functioning properly, if you get the solenoid to buzz. If there is flow control on these valves, they are opened wide? When the solenoid is buzzing, can you hear or feel water running through the valve? Was this system properly winterized?

If your water supply is ok to the valves, the electrical is functioning properly, the flow control (if so equipped) is open wide, and still no water to the heads, my first reaction would be that perhaps there has been some winter damage and you have leaks. Two clogged lines, unless its ice, seems highly implausible to me.