I dont think the booster would make that much of a difference when used witha Zenith, i would say the pads are the first thing to change, even without a booster you'll notice a better performing brake with some decent pads and a well set up brake. I guess you're using a smooth rim? Cleaned it recently? Personalyl i'd Personally i would buy some trials specifc pads intended for use on a smooth or lightly grinded rim, something like heatsink yellows are awesome, clean your rim with alcohol or even water and a clean rag, or grind it. Set up everything perfectly square and see where you are and if things ahve improved. Boosters tend to not have much effect on bite in my experience, but improve hold.