I haven't found a compressor necessary, myself... Petzl's maintenance instructions seem to be a generic thing for all their gear. Compressed air and power washers at high pressure can force dirt into bearings and stuff, especially if they're not sealed ball bearing units. At lower pressures, I've never had that issue. Still, for the ZigZag, I just didn't find it all that helpful, anyway.
WD-40 has solvents to help dry out moisture on steel components, but again... I haven't ever had it dilute out the grease in sealed bearings. You can get lithium grease in a spray can, and squirt a small amount into bushing/bearing surfaces and wipe off the excess.
I give the ZigZags and other mechanicals a good cleaning once a year, sometimes twice a year. The rest of the time, I keep a can of WD-40 and a small bottle of light oil with me. I just use the "compressor tool oil" used for air tools. If I get the device gunked up with sap or pitch, I hose it out of there with the WD-40 and wipe it down... then a little oil and wipe it down again. Takes about two minutes, if that.
The ZigZag handles sap and pitch better than anything else I have... but leaving it on the device is really bad... it gets thick and sticky and much harder to get off, and collects a lot of dirt and bark dust. Hence, the quick cleans on the job. If it does get nasty, I use a toothbrush and WD-40 to clean it up at home, then wash it in ordinary dish soap and hot water. Oil it, wipe it down.
I can tell you that I doubt if my method is Petzl approved. But, it's worked for me for the last five years, and I promise you that none of mine look like they've been used much. I think the wear that I see on other people's mechanicals is mostly from the dirt and grit getting pounded into the device from the rope-on-metal under tension. Keeping them clean is really worth the little bit of work involved. If the maintenance is cutting into your beer drinking time, just drink beer while you're doing it.
