In October '18, I started growing several Zelkova trees from seed. One of them, pictured below, is doing remarkably well. However I'm concerned about it's branching structure. Almost immediately from the start, the lead stem split off four ways. They are all about the same height and I can't tell which is the dominant. I'd prefer shaping this into a single trunk tree but am unsure if I should prune this early in life? If yes, is it too late to fix this? Any guidance would be much appreciated.