Japanese zelkova Loosing its leaves
This is likely a response to heat and drought and is somewhat normal for Zelkova as we head towards fall. They have enough leaves and it is late enough in the season that it is not of concern for the tree.
You may be able to lessen the leaf fall with supplemental watering during periods of drought. If it is the look that you don't like, don't bother to rake, just mow them and they will disappear into your nice looking turf with the added benefit of being a Nitrogen source as they break down.
We have had here in Maryland a ton of rain about 4 inches so I am pretty sure it is not lack of water.
also the leaf drop seems to start on the east side of the free which looses almost all the leaves then the problem gradually moves around the tree to the rest of the tree.
i have good drainage as the tree is on a slope so the tree is not standing in water
If the roots are somehow unable to make full use of that rain, the tree could still be suffering drought stress. Girdling roots at the base of the trunk, hidden under a buried root flare, is one possible explanation for this, along with prior over-watering (or excessive exposure, such as root zone flooding near that gully) that compromised the root system in an earlier year. Both can prevent sufficient moisture from reaching the canopy. Since roots on a tree this size extend well beyond the canopy diameter, a significant portion of its root system is within the "floodplain" of that depression, were it to ever hold standing water.
Other environmental stress factors, such as from increased summer temperatures, can cause premature leaf drop, though the later in the growing season this happens, the less impact it has on the tree's overall health. (Even an increase of just a few degrees can make the difference between tolerance and a stress reaction, especially over a prolonged period; we keep experiencing record heat in July in recent years, for example. The lack of sufficient cooling overnight, exacerbated by paved surfaces, can compound the problem, as it does not allow sufficient "rest" for the tree's metabolism.)
We do not know why the east side consistently loses leaves first; if there is a girdling root, the eastern side of the trunk would be the first place to look.
An arborist would be advisable to assess the tree in person at this point, as we cannot see any overt signs of pest or disease issues in the photos. The second and third links on this page direct you to search tools if you'd like help locating an arborist:
https://extension.umd.edu/hgic/topics/how-do-you-decide-when-remove-tree (this link is not meant to imply we think the tree needs to be removed). It's possible they'll recommend having a tree-care company air-spade the trunk base in order to expose the root flare and look for problems there.