Shouldn't be a problem. ANA is Star Alliance so UA policy is to check through on separate PNRs. It's even more likely since you're on ANA on both PNRs. Just allow a little extra time if the check in agent needs to get the Help Desk to give a blessing, I'd think that EWR does enough of them that they can just do it. When I was flying out of SMF and RNO sometimes things would need a little help with blending the PNRs.