Theoretically zero point energy is limitless. However, mainstream scientists doubt we will ever be able to effectively harness it. For theoretical, technical and even philosophical reasons. Be that as it may; the theory they invoke is misapplied, Technical considerations can be overcame, and philosophy has no place in determining a hypothesis' validity. ZPE can work and some mainstream scientists are slowly and grudgingly admitting there is something to it in terms of appplication.
All that aside, zero point energy gathering schema are unlikely to equal antimatter conversion in terms of energy density at any given moment. ZPE might be harnessed to power a ships systems or even ignite fusion reactors but to suggest they can provide the thrust of an antimatter explosion is a bit of a stretch. ZPE is definitely worth looking into but propulsion will not be an application. The cohering apparatus is too fragile to be near such violent levels of energy production.