I don't think Jordan joining would result in an easy victory for Israel, far from it. Peled's division is still on the border with Jordan, so he will be fighting there, instead of moving north a couple of days later. This means that while Israel has one division, with not many tanks, fighting Jordan, we also get less forces in the Golan for the counter attack into Syria. No doubt Syria would be pushed back, but it will not shorten the war. The war with Jordan would be over in a few days, after that Israel would keep Peled's division on the border. The war with Egypt is unaffected, as we are not talking about units that are diverted. The war ends on the same day. The difference with Syria, is that now Israel does not carve another chunk out of Syria, so perhaps the war of atrittion that kept going there up to 1974, will not happen. Syria might call it a day after Egypt throws the towl.