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The 'pro' method of dealing with this situation is to not use antisyphon valves. Instead, a RPZ backflow preventer in the supply lets you use ordinary zone valves, with no need to worry about elevations. However, this costs extra money, and slightly reduces the available water pressure in the zones.

There is a compromise of sorts available that does not require any supply plumbing changes. You don't need to relocate the antisyphon valve, so long as you add a vacuum breaker to the zone plumbing at the top of the slope, at a height that assures it will be functional. This would still have uphill water running back out of the ASV after the zone shuts off, but that could be remedied with an inline check valve in the pipe. The check valve would effectively 'disable' the ASV as protection, but the added vacuum breaker takes over the backflow protection job for that zone.

This compromise probably works best for systems with zones plumbed entirely in PVC, because it is basically declaring that the water leading to the uphill vacuum breaker is still potable water, despite the fact that it is downstream of an antisyphon zone valve. For the sake of plumbing integrity, use Schedule 40 PVC for the new upslope zone plumbing. (the polyethylene tubing - poly pipe - favored in some parts of the country for zone plumbing is more breakable, and less appropriate for this compromise approach)