Careful not to go too high on the zinc additive. My TB zinc plus would raise the ppm to more than 5000 if I used the whole bottle. Surely that would upset the oil's own additive package and overwhelm the detergency. It says to drain it out after 1000 mile break-in for that reason. I use only a calculated amount to raise the zddp content into the 1100-1300 ppm range. I recommend contacting the maker to find out what the zddp content is of an additive and making your own calculations from that if you're going to use any additive at all.
According to a reply from Lucas, the TB Zinc Plus is 38,500 ppm ZDDP.
I also contacted Redline about their break-in additive and they told me it was 17,000 ppm ZDDP.