Yeah, a lot of those rules are real head-scratchers the first time you see them! If you're trying to understand them, it helps to read the whole book.

If you look at them all together: don't weave linen and wool together. don't sow your vineyard with different kinds of seed together. don't yoke a young bull and an ass together... and oh, also, don't marry outside your religion. I think the ancient Hebrews understood these rules as all being related, and understood them on both a literal and metaphorical level.

Plus if you look at stories in the Old Testament, Israel is *constantly* getting in trouble with God for intermarrying and adopting the neighbors' religious practices. It was a big issue for them.