Contradiction with Proverbs 14:12
This verse speaks about the existence of ways that seem right to a person but end in death, contrasting with the uplifting imagery of making mountains a way in Isaiah 49:11.
Proverbs 14:12: There is a way which seemeth right unto a man, but the end thereof [are] the ways of death.
Contradiction with Isaiah 40:4
This verse mentions rough places being made plain and valleys being exalted, which might oppose the idea of making all mountains a way in Isaiah 49:11.
Isaiah 40:4: Every valley shall be exalted, and every mountain and hill shall be made low: and the crooked shall be made straight, and the rough places plain: [straight: or, a straight place] [plain: or, a plain place]
Contradiction with Matthew 7:14
It states that narrow is the way which leads to life, contrasting the idea of making mountains a broad way in Isaiah 49:11.
Matthew 7:14: Because strait [is] the gate, and narrow [is] the way, which leadeth unto life, and few there be that find it. [Because: or, How]