The z fold and flip are IPX8 rated, being as waterproof as any iPhone (i believe the 8 rating says 15-35 ℃, 86-106 kPa, fresh water, up to 1.5 m, up to 30 minutes). They have 'brushes' and seals to minimize the effect of dust particles and the hinge is separated from most electronics.look, manufacturers worked for multiple years to eliminate moving parts. even the home button - which got probably the most wear end tear in every device. if something needs to move, it will wear. this is exponentially true for this telescopic mechanism: let's just forget about the biggest culprit, the screen, and focus on the easy thing.
- the slides, rollers that require reliable "lubrication"
- dust, cloth fibres, random junk must be kept away from the moving parts otherwise those will clog (and you put your phone into your bag/pocket)
- fluids must be kept away, and yes, good bye water resistance (and dust resistance too)
- miniature servos are not rated for such frequent positioning, or special ones need to be developed which drives up cost
- the weight and internal space taken up by this elaborate mechanism
- when extended, the structural integrity of the device is gone
- i hate drop tests, but a device like this would score the lowest (this time legitimately)
- a wrong move, and you wreck the gears for good
so, looks good, but not a great plan

Samsung Galaxy Z Fold 3 drop test proves it's the most durable foldable yet
Samsung's Galaxy Z Fold 3 has survived another durability test with flying colors. The phone remained fully functional even after being dropped ten times.

Drop tests show its quite durable. The inner screen is technically flexible so doesn't crack like its glass outer screen.