Synonyms for With respect to:

adj.

concerning (adjective)
regarding.
regarding (adjective)
in relation to.
relative (adjective)
related, in regard to.

n.

with respect to (noun)
regarding, related to, in relation to, as to, concerning, vis-a-vis, with regard to, related, in regard to, with reference to.

prep.

apropos (preposition)
with reference to, as to, concerning, regarding.
toward/towards (preposition)
with regard to.

Other synonyms:

adj.
in regard to, in relation to.
prep.
as to, with reference to, with regard to.