Your toddler takes one long nap after lunch. Your baby takes several short ones scattered across the day. On a bad day the two never overlap, which means from the moment you wake until bedtime you are on duty for at least one child, and often both.
With two under two you are not going to sync every sleep, and chasing that will drive you mad. What you can do is build one reliable overlap.
Anchor the toddler, aim the baby
Fix the toddler's single nap to a consistent slot just after lunch, then treat the baby's midday nap as the thing you move. By nudging the baby's morning earlier or later, you slide their midday sleep into the toddler's nap, and suddenly you have a window with both children asleep.
Protect the overlap
Once you have it, guard it. Let the baby's other naps fall where they will and keep the shared afternoon window clear of errands. That one protected hour or two is what makes the days with two under two survivable.