I have tracked the problem of ZDDP for a while. Over on the Team Chevelle board they have huge debates that have settled on the following. Rotella has lowered it's zinc ratings so the best bet now is Chevron Delo 400. Also Penzoil GT Racing is high in both zinc and price. Harley oil is also being used for the ZDDP content.
If anyone is interested their is a sticky on their board with all the test results from the oils being used in high spring rated , Hydraulic cams .