[Vivtek]

The reason it "sounds weird" is that it's attempting to straddle two dialects. The use of "whom" is a signal for classical (Latinate) grammar, which would demand the Latinate prepositional word order, while the use of separable-prefix Germanic word order with "with" at the end is a signal to use "who" because dangling prepositions are associated with the less-Latinate trend towards discarding accusative "whom".

These modes normally don't get mixed, hence the weird sound of the title of this post.