[Answered ]-Use objects from one django model to filter objects from another django objects

You can do this in one query using double underscore notation and F expressions:

from django.db.models import F

route_points = RoutePoint.objects.filter(
    vehicle__travel__begin__lt=F("datetime"),
    vehicle__travel__end__gt=F("datetime")
)

then simply iterate over the route_points queryset:

for route_point in route_points:
    print(route_point.vehicle, route_point.point, route_point.datetime)

You can filter the Travel Queryset:

start_date = '2022-12-30'
end_date = '2023-01-06'
travel_qs = Travel.objects.filter(begin__gt=start_date, 
end__lt=end_date).values('vehicle_id', 'begin', 'end')

Now you can use travel_qs to retrieve the Points from RoutePoint:

route_point_qs = RoutePoint.objects.filter(vehicle_id__in=travel_qs.values('vehicle_id'),
                                        datetime__gt=travel_qs.values('begin'),
                                        datetime__lt=travel_qs.values('end')).values('vehicle_id', 'point', 'datetime')

I did it like this:

    vehicles_with_dates = travels.values('vehicle_id').annotate(min_dt=Min('begin'), max_dt=Max('end'))
    route_points = RoutePoint.objects.filter(
        vehicle_id__in=vehicles_with_dates.values('vehicle_id'),
        datetime__gt=vehicles_with_dates.values('min_dt'),
        datetime__lt=vehicles_with_dates.values('max_dt')
    )

It worked perfectly fine, thanks to Iqbal Hussain.