Hello,
5600MHz is the max frequency for the i9-14900HX in this laptop but running 64GB is not a straight answer as 2x32GB can work at 5600MHz or may not. This part comes down to the laptop itself and everything that may impact the memory operation (signal quality), like the dimm slots, motherboard, CPU, build design and quality of soldering / PCB design...
Assuming the above is all fine and the memory module / chips are compatible this will actually work fine but it's something you will need to try for your one / laptop. When installing new memory the motherboard will actually enter a test phase "memory training" which is designed to try and establish the memory running parameters and maximum frequency for subsequent boots. During this phase the motherboard can actually make some adjustments to help correct any timing / signal issues but if all fails it will downclock.
Consider memory from G.skill, Mushkin and Crucial (not Kingston unless you know they are using SK Hynic chips).
Hope that helps.
