This is not a well-written question, but whoever wrote it is likely trying to get you to understand that a zoning ordinance is a key piece of enforcement for land uses, whereas the comprehensive plan is a higher level planning document that is essential a guide for policy.
So if "the proposed use conflicts with the zoning ordinance, even though it is consistent with the comprehensive plan" the owner would either not be able to pursue the intended use or apply for a zoning variance to allow for the intended use.
Asking if "the proposed land use is inconsistent with the comprehensive plan but complies with the zoning ordinance" is sort of nonsensical insofar as it doesn't matter. The comprehensive plan isn't a document used for enforcement, so the owner would just ignore the comprehensive plan.
Is this a multiple choice question - because asking how the landscape architect could assist is far too broad. They could help apply for the variance, they could advise the owner on the correct course of action, etc.