Mechanical confusion

So, I allow certain homebrew and third party classes and races at my table. I have a preapproved list, in fact. I also make my own content. Recently, a player brought this to my attention and asked how they would interact.

The first comes from the Path of Thunderstorms Barbarian, from Monkey DM's Tome of Vile Corruption:

When you deal damage with a weapon you can choose to force the creature to succeed on a Strength saving throw (DC = 8 + your proficiency bonus + your Constitution modifier) or be pushed back 10ft.

the second part comes from the Stormborn Orc, a subrace I made for my Untamed Wilds Sourcebook I'm working on.

When you move at least 20 feet straight toward a creature and then hit it with a melee weapon attack on the same turn, that target must succeed on a Strength saving throw (DC 8 + Strength modifier + proficiency bonus) or be knocked prone.

Question from the player: "If I have two features that force a creature to make a save or be pushed back, what happens if I use them both on the same attack? Do they roll two saves for two different knock-backs or one save for both at the same time?"

How would you personally rule this? Is it one save for both, two separate saves, or does only one of these effects take place?